Emissions and Exhaust Systems

Internal combustion engines have byproducts called emissions. These byproducts are either particulates or gaseous chemicals. Emissions travel from the engine via an exhaust system, which is a system of pipes that leads the emission away from the combustion source.

2,438 Questions
Emissions and Exhaust Systems
Mufflers and Tailpipes

What can cause white smoke from the exhaust?

Here are the best answers compiled from s.com contributors:
  • It often means that you are burning antifreeze. You asked if it needs antifreeze, have you noticed any leaking out of the reservoir tank while you are running it? Sometimes when the head gasket goes it will produce a passage for the antifreeze to pass from the capillaries into the combustion chamber. It is easy to check if you have an air compressor. Remove one of the rear sparkplugs and the radiator cap. Fill the radiator and then push some air into the sparkplug hole (get a good seal in case a valve is open). Repeat with all the cylinders and watch for air bubbles coming up into the radiator. If bubbles come up or fluid is pumped out, the head gasket is blown and must be replaced. It is more likely to happen at the back of the engine because it is farthest away from the fan and therefore gets less cooling. Also check your oil for discoloration. If it is a brownish color it could mean your oil and antifreeze are mixing and has the potential to damage your bearings.
  • If the exhaust billows white smoke for a few seconds when first starting the engine after it has been sitting for a while, such as overnight, and then runs normally, it could mean that the rubber valve stem seals have perished - especially if the vehicle is a few years old and has done over 60/70,000 miles. Another clue is: does the exhaust smoke smell like fresh, rather than burnt oil.
  • After going nuts trying to figure out sporadic tailpipe smoke on my Nissan Maxima, with no other negative engine symptoms, I eventually stumbled upon a malfunctioning PCV valve. The ball-check wasn't fully seating, allowing small amounts of oil to sneak past and into the combustion chamber. A cheap and easy fix.
  • White smoke or semi white can be produced in several ways. One way is oil this is normally a whitish blue to blue smoke and has the apparent smell of oil being burned. Next could be antifreeze when it is being burned it has a sweet type of smell and tends to dissipate in the air rather quickly. Next is automatic transmission fluid which is normally found on automatic transmissions and its normally drawn into an engine thru a vacuum line via a defective transmission modulator valve or some other defective part. Transmission fluid is very apparent and billows out so bad that you can't see anything behind you. Last but not least another type of smoke that is not white but black is the presents of to much gas/fuel being burned in the engine. PS the one good thing about transmission fluid being burned is it is an excellent way to clean the carbon out of an engine.
  • Black smoke is burning oil. Blue smoke is usually transmission fluid due to a leaking modulator valve in the older auto transmission. White smoke is due to water getting in to a cylinder from a bad gasket, cracked block or a cracked head. cracked heads. Mine started misfiring, with new plugs. Smoke came out the exhaust. Result, low compression in the cracked head. When car was cold it ran fine. After it got hot, the crack in the head would open up, hence, sputtering. I've had to replace 3 heads. Everytime I've had to have this done, I had to buy a whole new head gasket.
  • After extensive research I came to the conclusion that TOO much oil is also a main culprit for white smoke out of the exaust.
  • I changed the PVC valve, the breather and the air filter and it's good as new.
  • There are a lot of incorrect answers here... but for the most part, you can hold true to these: Blue smoke is primarily from internal engine wear. If it's constant when the engine is on, then the rings etc are worn and need to be replaced. If it only is blue when the engine is cold or first started, the rings are worn but not gone completely. You get the oil seeping during the night and it burns off when the car is started in the morning. Black smoke is a fuel/air mixture suggestion problems with injection or carburation. Cause of black smoke is due to running rich in the fuel air mix. White smoke can and DOES come from coolant burn off in the oil due to a leaking or blown head gasket, cracked head etc. If you aren't sure or you don't know what you're talking about, don't advise. Wrong advice can be more damaging than the actual problem.
  • White smoke is caused by engine coolant/Antifreeze being processed in the combustion chamber(s) of the engine.....ie burning, melting, frying, whatever....Period....I'll explain further.... This is automotive chemistry 101....Oil of any automotive type burns blue.....too much fuel issues burn black not enough fuel issues burn grey on a cold day you may see what appears to be white smoke from the exhaust that will disappear after the vehicles engine has warmed up to it's normal operating temp.. This is a normal reaction called condensation... condensation is the result of a small amount of water/dew being drawn into the exhaust usually collecting in the muffler and/or the catalytic converter and is caused by our friend mother nature..... like when you see your breath on a cold day...
  • I am a highly experienced ASE certified automotive repair tech. I have over 16 years of diagnostics and repairs to my credit..I have made a very good living in the automotive business by being precise with my diagnostic procedures....I have worked for 3 of the largest rental vehicle companies in the country.... I have diagnosed and repaired an estimated 200 vehicles to date with the white smoke issue... every vehicle that i mentioned had engine coolant/antifreeze entering one of the combustion chambers in the engine... Most of these vehicles had a damaged head gasket(s).. the most common causes of this issue that i have detected over the years are due to improper maintenance of the engine cooling system, severe overheating of the engine, improper tightening of the cylinder head(s) during an engine overhaul,or some other type of repairs that required the head to be removed and also defects in manufacturing of the gasket or the engine... i have seen evidence of careless repair techs that have scratched or cut the surface of a replacement head gasket with either a tool or the cylinder head during the install process.. sometimes it will never cause an issue but it can... i am very careful when dealing with any gaskets but especially head gaskets due to the amount of work involved in replacing one on some vehicles.. bottom line, I'm not fond of doing the job twice so I'm careful the first time... I have seen improper cylinder head or engine block servicing techniques cause failure of the gasket(s) these types of failures are generally caused by improper cleaning of the gasket surface of the engine block and/or the gasket surface of the head.. i have also repaired or replaced cracked heads and in extreme scenarios i have replaced cracked blocks and severely overheated engines with a new or re-manufactured engine due to such severe damage to the internal engine components or block .. There are a mix of correct and incorrect answers to your concerns by the participants that have replied.. I can assure you that almost every well trained tech will answer your questions as i have.. I'm not saying I'm an automotive god, I am just proud of the priceless knowledge that i have acquired...FYI, I'm a graduate of Denver Automotive and Diesel College in Denver Colorado.... DADC is one of only two Automotive Technology colleges in the country with the intense hands-on and classroom teaching practices to properly train a truly, highly skilled automotive/diesel tech who can easily handle any diagnosis and proper repairs of yesteryears and today's automobile technology....
  • White smoke CAN be caused from oil....I have fast-road engined 1987 Golf Mk II. If I boot it hard on tight corners, roundabouts, etc, it can cause oil surge in the engine and some oil can 'slop' into a cylinder. The James Bond style smokescreen it produces can be very exciting for drivers behind me!
  • Lots of good answers; I just want to see if I can clarify from my experience. SMELL!! Good mechanics without great diagnostic tools learn to SMELL. "Burning" (yes, technically it's boiling, not burning) Antifreeze smells 100% different than burning OIL. Let your nose be your guide. The Antifreeze will have a sweet sort of smell--hey--kinda like antifreeze smells, and it will make your eyes tear up and your throat lungs will tell you to get out of that toxic fog right away. Also--the timing. Yes, when forming a good question, you need to give GOOD DETAILS. Does it ALWAYS burn white? Just at startup? Only when hot? Etc. DESCRIBE, DESCRIBE, DESCRIBE!!! A head gasket problem is ALWAYS there and it only gets worse under pressure/acceleration/load. It will go from a little cloud to it's own weather system when you stomp on the gas.
  • OVERFILLING THE OIL will produce this white burned smoke too. Yes, it will SMELL different. IT will also usually go away after some driving. CHECK THE DIPSTICK, it's obvious, but do it--do it right. Flat surface; cold engine. Pull--Wipe it off--put it in--now you are getting the real level. Oil burning will be at startup from worn valve rings/seals and during driving from overfilling at first a lot, then only at heavy acceleration/g forces when demand is high. Again--smell, check all your fluid levels (OIL, WATER, TRANS) of course, whatever is low is what you are BURINING (or for the one gent that gets particular, boiling). ALWAYS Start w the simplest thing or the cheapest. Did you just change the oil and it started--overfilling, etc. Yes, it won't hurt to check the PCV valve and tubing. Really, check all you can check.
  • My problem with white smoke was whenever I would be going down the road at high RPM and let off the trottle. Then it was like a smoke bomb went off. Bottom Line.......... My Vacuum Modulator went bad on my transmission whenever high vacuum was created it was sucking transmission fluid into my intake manifold and thus into my combustion chamber creating white smoke. Replaced the modulator for $12 and everything is right with the world
  • i had the exact problem with my Mazda down to a T. All we had to do was buy a bottle of engine sealant... it takes a full day to run thru so follow directions exactly. Now the car has no problems... full power is bacl no more "smoke bombs" and no more dying at strange times.
  • Steam or smoke is the question here. If its steam some considerations are what year is the vehicle newer catalytic converted cars emit steam and water from the exhaust and you should be cautious about the blown head gasket or cracked head syndrome, if you suspect a blown head gasket or cracked head go to a reputable shop that can confirm exhaust gasses in the coolant. You will notice a low coolant level and a peanut butter looking substance on the oil cap (possible traces of water and coolant in the oil but generally engine pressures will prevent this. Be prepared for the worst and hope for the best. If it is smoke a thick white smoke it could be transmission fluid being pulled up through a vacuum line to the intake manifold and being burned, this was quite common on older Ford and Chrysler vehicles that had a vacuum shift solenoid and an automatic transmission.
  • Has your car severely overheated recently? Does the smoke smell like antifreeze? If it does, you probably have a blown head gasket. The "smoke" in this case is actually steam from water leaking into the cylinders. Also check for yellow or white goo on the oil cap and dipstick, indicating water leaks to the oil.
  • Your symptoms are indicating a possible head gasket problem. You have water going into the combustion chamber and coming out the back tailpipe as steam. You may also have exhaust gas in the water which can also be checked by a mechanic. Be prepared for the expense of a head gasket or possible engine replacement.
  • If it is not happening all of the time at operating temperature (head gasket as mentioned before) and it occurs just at startup. It may be that due to heavy moisture in the air, dew, a heavy rain, will build up moisture in your exhaust system. At initial startup until the vehicle is warmed up and run for a bit, you may see thick white smoke.
  • I had an old engine that sucked oil through an intake valve when the engine went fast enough. If you burn enough oil it looks white. Especially in Michigan on a cold morning.
  • I had this problem with my '96 Ram after an overheat. A cracked head gasket was allowing antifreeze to get into the combustion chamber and creating all kinds of white 'sweet smelling' smoke.
  • White "smoke" in cold weather is just steam. When gasoline ignites it produces quite a bit of heat and expands to several times the original size, creating high pressure on the piston. That pressure causes the piston to move down, turning the crankshaft which makes the car go. When the fuel ignites it causes a sudden and violent chemical reaction between the the oxygen in the air and gasoline (which is a long chemical molecular chain of carbon and hydrogen) resulting in carbon dioxide and water vapor. As the water vapor cools in the exhaust pipe it starts to form small droplets that are visible in the form of steam vapor. That's the white smoke. Once the exhaust pipe warms up sufficiently, the exhaust leaving the pipe is still hot enough that the water vapor hasn't formed the droplets and dissipates quickly enough that you don't see the vapor. On the other hand, if it's light blue or blue-grey smoke and it doesn't stop when the exhaust pipe warms up, that's oil vapor and a sign of bad rings and/or valve stem seals.
  • white smoke is usually caused by condensation in the combustion chambers. This will usually dissipate once the car has warmed up. If it persists there could be difficulties with: Problem: Solution: Moisture in fuel Apply one cap full of Methylated spirits to fuel tank (This is quiter safe by the way, it dissipates water) Head gasket leak Replace head gasket, approx $500 AUS (other symptoms such high temperature will also be prevailent.) Failing these two suggestions, there is a slight chance of moisture in the oil sump. this is rare if the head gasket is ok. Simply check your oil level, if the oil looks milky, there's the problem. Also if it is milky, replace the head gasket.
Emissions and Exhaust Systems
Oxygen Sensors
Air Pollution

How has technology affected car pollution?

It has radically reduced the emmissions given off from automobiles. Too bad the big vehicles aren't as closely scrutinized yet.

It is absolutly amazing. From a seminar recently, I understand that leaving the fuel cap off will release more hydrocarbons than from the exhaust out the tail pipe.

With the addition of flex fuel, electric, propane, hydrogen, bio-diesel, and Hybrid cars the outlook is better.

I have found that since the advent of OBDII the number of problems that can occur is astronomicle. I have a pre-OBDII and an OBDII vehicles,and by comparison (Both being Fords) the OBDII has suffered more problems (From very low MPG to extremely bad performance issues not able to be corrected by Ford engineers themselves). At any given time the dealerships claim it is in the computer program to which they can not change(Poor MAF sensor performance,Timing issues)they just don't seem very knowledgeable about what they are doing or care about the matter (You already bought it tough luck is the usual answer).But their resolve to the delema was to go online and purchase a chip for socket J2 on the computer,I asked if the vehicle does not get 21M.P.G. like the manufacturer states than to me there must be a problem. After the techs laughed they stated that there is no possible way for that vehicle with that program to attain that fuel economy.It was stated that 18 M.P.G was the best I'd ever see. Not accepting this from Ford I set out on a little adventure, and discovered their big flaw. It was the catalytic converters, and by having four of them would be a strain on any engine. So we decided to test our theory,and removed the larger segments of converters (2 of them). Created a filler pipe to cover the distance, and re-inserted the O2 sensor as to not throw a code. Discovery was the fuel economy went from 18 M.P.G. to 26 M.P.G. This was a very large jump in fuel economy. To test this out I had to do it several times on over the road tests, and the results came out to within a few tenths of a M.P.G. of each other. So, in removing the technology and applying some old fashioned know how we were able to make the vehicle perform better and be more economical than the manufacturer could. (And by the way Ford blames the E.P.A. for their bad designs). JIM

Auto Parts and Repairs
Emissions and Exhaust Systems

What are signs of an exhaust leak?

Headache Nausea Sleepy Dizzy Death All from carbon monoxide poisoning

Emissions and Exhaust Systems
Chevy Silverado
Ford Ranger XLT

Why would your engine smoke?

Smoking EngineHere are opinions and answers from FAQ Farmers:
  • Your engine would smoke if you are running at too high RPM or have had your RPM at a high level before. The engine is getting overheated. When you say it only smokes until about one mile it sounds like a problem with the engine. starter.
  • I would guess that its parents probably did and it learned it from its environment. More realistically, is it white smoke you see? And I would further guess that you have a 3.8 motor. If this is true, plan on a head gasket job and shave the heads. $1200 to $1400 if a shop does it. Or stress, frustration and possibly as much if you do it and it doesn't go well!
  • I doubt it's the starter. You probably have bad valve guides. Oil slowly runs down your valves after the engine is off then burns away as you drive. It stops after a mile because oil pressure keeps them sealed. If you had bad rings it would always smoke or always some when you decelerate at high speeds. Closing the throttle at high speed created high vacuum in the motor and suck oil up past the rings into the combustion chamber where it burns.
  • One or more oil rings are bad.
  • Valve seals become brittle and need replaced at about 100,000, sooner in hot climates. Rings will also make it smoke, or raw gaz puddling in the intake manifold if carburetted, excessive crankcase pressure will force oil past the rings if the system does not have relief through the pcv valve.
  • Unfortunately--That 1st answer is BAD (in this case). Overheating right at start up--Hey--On Planet Earth, engines don't overheat right at start up. Of course, physics and your temp gauge will confirm this fact. The too high RPM isn't too bad, but again, not the answer. I'm sure it smokes at low/high idle until warm. BINGO--The VALVE guys all have the right answer, in my opinion. There are other reasons it might smoke, as given, even overfilling; but from your description, it's the valve seals! They smoke when cold on start up then go away. It will get worse and worse. Budget about $400 from a mechanic that charges merciful rates.
  • First of all, the only Correct answer to your question is that your valve seals/Guides need to be replaced.Oil is leaking down the valves when the engine is cold and dripping into the cylinders, thus burning off after the first mile you drive.As your engine warms up and the oil burns off, the smoke will disappear. You will have this problem after your car is sitting for a while or on cold starts. Just for knowledge, Blue smoke is burning oil. Black smoke means over fuelling or air restriction whih means to much fuel. White smoke means burning antifreeze or water which is caused by a bad head gasket. By the way, the first two answers to your questions are completely out to lunch, These people have no business answering automotive questions.
  • I have a truck that does the same thing. It recently passed a CA smog test despite the huge amounts of smoke it puts out after first starting. The smoke is white but I can imagine someone describing this as "blue". The obvious reason it is smoking only after it starts was stated by the guy who said valve guide seals. Oil is pumped up to the top of the cylinder head above the valves and cylinder pressure (not oil pressure) keeps the oil from flowing down into the cylinder. When you turn the motor off it runs down into the cylinder. When you go to start it the oil burns up and comes out as smoke. My car also diesels and back fires when I shut it off. It does not run very well on oil but it will run for a while. This will cause your plugs to foul early and you will burn more oil than usual. The repair requires removal of the cylinder heads...usually. That's my 2 cents worth. The other answers are incorrect and are not even close. I admit I could be wrong but I know it's a pretty good guess...it seems several others here have the same opinion.
  • I had a Mazda that lost power and would smoke a blueish whitish smoke and later started to die. Turned out a bottle of engine sealant did the trick.
  • Additionally, the thumb rule is that: white smoke is usually caused by coolant water (or antifreeze) entering the combustion chamber; blue smoke is essentially due to oil (lubricants) getting in to the cylinder; and black smoke is generally because there is too much fuel (Diesel / Petrol) being inducted / injected in to the engine. And grey smoke would be due to a mixture of water and (excess) fuel entering in to the combustion chamber.
Emissions and Exhaust Systems
Head Gaskets and Valve Covers
Mufflers and Tailpipes

What causes a car to throw white smoke while driving it?

White smoke is coolant entering the combustion chamber. You have a blown head gasket. STOP driving this car immediately or you will destroy this engine. The head gasket must be replaced.

Emissions and Exhaust Systems
Oil and Oil Filters
Oil Spills

What is an oil catch can?

An oil catch can is used in turbo applications, or high-performance race applications where excessive blow-by (leakage past the piston rings) of air and fuel vapor occurs. This creates a positive pressure in the crankcase. Engine manufactures have placed a valve on the engine block which releases this pressure. This valve is known as a PCV (Positive Crankcase Ventilation) valve. During engine operation, blow-by gases, as well as oil mist from the rotating components of the engine, pass through the PCV valve and are routed back into the intake for the engine to burn off. However, some of the oil mist and other products settle along the engine intake and over time form a "gunk." The oil catch can collects the oil mist and condenses the fuel vapors while allowing "cleaner" gases to be passed back into the intake. Typically the blow-by gasses are passed through a wire mesh, which give the vapor droplets something to adhere to. Since the oil catch cans condense the vapor portion of the gasses, they will need to be drained periodically of all the oil, fuel and other contaminants.

Cars & Vehicles
Emissions and Exhaust Systems
Head Gaskets and Valve Covers

Why do cars smoke?

Assume you mean that it's burning oil. Typically that's because of poor maintenance or abuse.

  • There are several reasons that an engine will burn oil and most of the time these are caused by inadequate oil changes:
  • poor piston ring seal (cylinder taper, worn rings and/or carbon deposits in the piston ring grooves.)
  • Worn or faulty valve guide stems
  • SOMETIMES bad rod bearing can cause pistons to vibrate, allowing too much oil to remain on the cylinder walls.
  • A cracked piston can also cause quite a bit of oil burning, but that's quite rare.
BUTSometimes a sticking injector or a plugged air filter will cause a "wash down" situation, in which too much fuel gets into the cylinders, the fuel mixes with what little oil is on the cylinder walls, and the fuel and oil burn.


White smoke indicates coolant entering the combustion chamber. Normally caused by a blown head gasket or cracked head. Blue smoke is oil burning, and black smoke is an overly rich fuel/air mixture.

IFit's black smoke (too much fuel) it can be caused by a sticking injector, faulty sensor or plugged air filter.

Note that if coolant is entering the combustion chamber there will be other indicators, such as serious misfiring and/or coolant will be blown from the water jacket. Without those indicators you are probably not getting water in the combustion chamber

Emissions and Exhaust Systems
Air Pollution

What kind of car gives off the most air pollution?

Due to E.P.A regulations all modern cars must fall into a certain range. There is no particular vehicle that is allowed more or less per say.

Pre-92 non-obd2 equipped vehicles will have higher emissions than obd2 or CAN complaint equipped vehicles.

Race vehicles are not required to have catalytic converters equipped, and as a result will have higher emissions.

Epa link for fuel standards for passenger vehicles.

Auto Parts and Repairs
Fuel and Engines
Emissions and Exhaust Systems

What could cause a car to run sluggish then make knocking noises have white smoke from the engine then die and not start again?

Check your oil,- is it foamy?

Examine your coolant. Does it smell like oil?

Is the smoke sweet smelling?

Knocking has nothing to do with a head gasket, sounds like you have multiple engine issues to me.

And finally...if changing a head gasket is simple, why does it cost so much? because if you don't work on cars all the time it is most definitely not simple and includes timing belt removal usually.

Overheating can cause knocking. then refer to the above....

Your best bet is to replace your motor because usually the knocking noise is caused by a spun bearing which would cost a lot to repair.

*** New Below ***

The white smoke is from a blown headgasket, your coolant is leaking into one or more cylinders and that's actually steam that you see coming from your tailpipe.

When this happens, your coolant level drops (because it's pumping it out the tailpipe), your car overheats, and of course it will knock as it overheats. An overheated car is sluggish, as well.

Another bad thing that occurs by driving a car with this problem is that the coolant is washing the oil off your cylinder walls and your rings will tear up your cylinder walls as they self-destruct.

Head gasket replacement is not an easy fix nor is it cheap, and usually you'll need to get the head machined to make it perfectly straight again - heads warp from overheating. A good mechanic can do a head gasket replacement in a few hours.

- Dazani

This soudns like engine failure. Probably blew head gasket and ruined the engine due to it being run with bad head gasket too long.

You can find a god used engine with lower miles for around 800 at the most. usually more around 500 or 600 at most yards if you call around.

Labor to replace an engine we charge about 300 to 400 usually.

The car may not be worth doing this with however, some are not.

Most are though, if clean straight and drove fine.


If your vehicle has a Diesel engine, then you may just be looking at 'fuel starvation'! All of the above are to a degree correct - but unlike Petrol engines, Diesel engines are also known to emit white smoke through the exhaust system when fuel delivery to the cylinders is restricted and give off the same appearance as a head-gasket problem.

This could also cause 'sluggishness' or lack of power, bad starting or non-starting and also a low type knocking noise.

Change the filter and check that the fuel lines are not clogged or restricted; you could even possibly run your own fuel supply line from a can to check this part out if it's easier for you!

Start the engine and rev it at about 3,000 rpm for a few minutes or take it for a short drive to see if it still loses power, if it still does then assuming all has been changed and cleaned, you might look to see if there is something in the fuel tank that could be blocking the supply pipe!

Emissions and Exhaust Systems

What can cause blue grey smoke from the exhaust?

You're burning oil. either your piston seals are not working or you have other seals that have gone bad resulting in oil entering the combustion chamber.

Emissions and Exhaust Systems
New Jersey
Antique & Classic Cars

Does a classic car have to pass emission inspection?

If it didn't have emissions controls from the factory you don't have to pass any emissions test, check with your state as some are different, especially California.

Cars & Vehicles
Auto Parts and Repairs
Emissions and Exhaust Systems
Check Engine Light

What part would make your car not pass smog regulations because of hydrocarbons?

Perhaps this may help you in your search for causes. A high hydrocarbon reading is usually unburnt fuel. If the CO reading and the NOx readings are below the limit then look towards an ignition problem as being the most likely culprit. As the prior answer suggested, start checking items and begin with the basics. Year, make model, engine size, options, symptoms etc will help you get a more accurate answer next time.

Check the plugs first, all of them! One bad plug will give you a miss and everytime the car misfires unburnt gas goes into the cylinder and out the exhaust which raises the HC. Same goes for the wires (check resistance with a multimeter) check the distributor cap & rotor (if applicable) for cracks, corrosion or burnt areas. Might want to do an injector service (if applicable), a sticky injector might put fuel in at times when its not supposed to and up goes the HC. If the check engine light is on 1st thing to do is pull some codes and this will give you some direction. Codes can be pulled manually by using the diagnostic connector or a scanner.


High hydrocarbon levels are also seen with a much too lean mixture. If you are looking at an older carburated car, check this first. A lean mixture will not burn completely, and unburned mix goed out the tailpipe. An overly rich mixture burns fine, but to carbon monoxide, not dioxide. So a rich mixture will fail on CO, not HC. This is the reason for the vacuum hose fix - it cuts down the amount of air entering the engine, while leaving the fuel the same ( or increasing it a little if the leaks are really bad ). This said, the ignition system is also suspect, as any misfire will increase HC. So, check your vacuum hoses (lightly spray connections w/ carb cleaner, an RPM increase means a leak), change your plugs and wires if they're more than a year old, and richen the mixture a hair if this adjustment is available.

More Information:

I had to replace a lot of vacume lines to get mine to pass. It also could be o2 sensor, bad spark plugs, rich idle(too much gas), bad spark plug wires, bad injectors(or carburetor), bad ignition coil/cap/rotor(weak spark), bad catalytic converter/clogged muffler, exhaust leak, etc.

Emissions and Exhaust Systems
Mufflers and Tailpipes

Will bad rings cause blue smoke from exhaust?

Stuck or broken oil rings can cause blue smoke.

Emissions and Exhaust Systems
Check Engine Light

Will a bad egr valve cause check engine light to come on?

It can.

Emissions and Exhaust Systems
Head Gaskets and Valve Covers
Mufflers and Tailpipes

What would cause white smoke to come out of the tailpipe?

If you are having a lot of white smoke all the time the car runs then check for coolant mixing in with the oil,look for water in the oil when you check the oil or milky brown oil. This produces a white "steam" that is very thick to come out of the exhaust. If your engine temp. gauge is very high and over heats you probably have a blown head gasket. If it has a bluish tint look it may be burning oil. Indications might be how much oil is currently in the car i.e too much oil, or if there is a leak in the line you may be adding a bunch of oil over a short time. If it is only when you first start the car and the engine is cold, then it may be that your valve seals are bad and need replacing. Hope this might help or at least give you some ideas...

AnswerIt's coolant. headgasket, cracked or warped head, intake manifold or gasket, or cracked block are your sources. Take it to a care car service to have it checked AnswerAre you sure the smoke is white or is it a light blueish color start the car and have someone stand in a position to see the tail pipe and see if much water comes out with the smoke if it does and you have been running low on antifreeze i would say a head gasket if no water and not low on anti freeze look at worn valves or valve seals or worn rings good bet on these two items good luck AnswerBurning oil in the fuel would cause black smoke so it definitely has nothing to do with that. White smoke can be caused by water in the combustion camber or unburned fuel. If you've be having bad gas mileage you probably have a problem with your fuel or ignition system or timing. You can usually smell the fuel in your exaust when this happens. If you smell no fuel and you've had no change in fuel economy check for water like one of the previous posts said. AnswerTry the changing PCV, it work for me when white smoke(rock concert-like) would come out of the exhaust every time the car was turned on. That was the only time the white smoke would come out in my case. If it is a constant white smoke emitted from the exhaust, especially while driving, it could be something else. AnswerOne thing that I noticed, is that when valve seals get some years on them, a little bit of white smoke can emitted from the tail pipe when you first start it up or when you set at a stop light idling. But usually not that much smoke. Old valves could be causing you to run rich. AnswerSomehow water has or is being burned,check coolant level and temp if you have temp light put a guage in if coolant low there is your problem if not check egr valve and pcv valve also check oil level if high and milky there is high possibility that you have blown head gasket and or block may be cracked allowing oil to get into the oil pan. Answeri think it would be a blown head gasket or blown head
Emissions and Exhaust Systems
Heating AC and Engine Cooling
Mercury Sable
Heater Cores and Blower Fans

What would cause white smoke to come out of heater vents?

Most likely the heater core is leaking. If there is also water on the floor and an antifreeze smell in the passenger compartment, those are also signs of a cracked heater core. Also, GET THAT TEMP GAUGE FIXED!!! You could be overheating and not even know it. Once the motor overheats, you're risking a blown head gasket, a VERY EXPENSIVE repair, or even worse, a blown engine. If steam is coming out of the vents it is very possible the motor is overheating. You need two repairs, your heater core and your temperature gauge.

My heater core was replaced since it had a hole in it. The blower was also replaced but with a used one. The guage is now working and so far, no more white smoke. Heater does not get hot though and the blower motor is very loud. Hey, ya gotta laugh a little...from one thing to another. I suppose the worse thing is over. Thank the Lord though I did not have a new car since the guy that worked on it did a number on my dash.

Symptom: on a 2000 Ford Contour, white smoke came through the vents and the smeel was acrid. We switched the car off. A few hours later, the car was fine, no more smoke, but the heater didn't work on one speed setting.

Solution: there is a resistor block which controls the blower speed in the ducting. When one of the resistors goes, white smoke is fed dirrectly up to the vents. Replacement is easy (admittedly while doing a head stand in the passenger footwell) and fairly cheap.

Suggestion: many other cars will have a similar layout. Check this out before investing in a new heater core...

Cars & Vehicles
Emissions and Exhaust Systems
Oxygen Sensors

Why would a car smoke when it idles?

I am no mechanic but with my problems with my car all everybody told me is there are several things you can do to stop it:

Get a fuel injection flush.

You have a lot of carbon build-up, try getting your car on the open highway. What you will be doing is blowing all the old carbon out and it should run better after that.

Your car might be getting too much gas at idle, OR your oil pump isn't working correctly. Which means the pump is putting too much oil to the cylinders when you idle.

Worn Valve guides (seals) cause an engine to smoke at idle, when the vacuum is strong enough to pull oil past the worn seals. Generally, the smoke will be bluish and will billow out when taking off after idling. I also have the same problem & I think it's my oil rings

Emissions and Exhaust Systems
Head Gaskets and Valve Covers
Mufflers and Tailpipes

What does blue smoke from the exhaust mean?

Well unfortunately you can count on it meaning you'll have to get your wallet ready for a workout. Blue smoke could indicate a few different things I guess. However it is my own experiences that tell me what is happening is your motor oil is leaking past your piston rings and getting into the engine cylinder and mixing with your fuel and ultimately burning along with the gas. That leakage is getting compressed with the gasoline in the combustion chamber and the burned oil makes the blue smoke. Your car probably also doesn't have as much power as it used to and is probably running rather rough too. If it isn't yet it wont be long and it will evetually cause the oil to break down loseing its viscocity and not properly lubricateing the pistons. Because what is also happening is some of the gas is leaking past those rings too in the opposite direction and mixing with the oil in your crankcase and thinning it out. When this happens the engine will overheat from excessive friction and it will seize.

They used to do ring and valve jobs to fix the problem. But that is "old school" and we now live in a disposable society and most every shop around will recommend a newly rebuilt engine. With shop rates being as much as $125 an hour, the rebuilt motor is much more cost effective. I'm sorry to be the messenger of the bad news.

This means that you should just sell your car while you can, so that you don' t get stuck with it.

Emissions and Exhaust Systems
EGR Systems
Honda Prelude
Ford Expedition XLT

How do you replace or clean an EGR valve on a 1998 Honda Prelude 2 2L?

Most EGR valves must be replaced with factory dealer parts in order to pass state emissions. Aftermarket valves will not pass the test. Keep this in mind when you finally replace it. Sorry I cannot give you details on how to do it.

The typical EGR valve can be cleaned and possibly repaired in some cases. Carbon build up can be scraped and blown out with compressed air.A pinhole in the rubber diaphragm (a common problem)can be fixed using high temperature silicone sealant. Locate the hole with soapy water while blowing into vacuum hose. Clean area with alcohol and let dry. Apply silicone sealant with a toothpick to the hole while sucking on the vacuum hose to draw the sealant into the hole. Let dry overnight. Such a repair can last many years and pass SMOG testing easily, saving the owner hundreds of dollars for parts and labor.

Emissions and Exhaust Systems
Mufflers and Tailpipes

Why would gas come out of the exhaust pipe?

Don't want to doubt you, but I'd definitely check to make sure it feels lightly oily or even soak some a few drops into a paper towel and see if it ignited (careful of course). Assume it's not running rough / missing occasional firings, right?

This can also be caused by a defective fuel pressure regulator. (Ford Ranger)

Emissions and Exhaust Systems
Catalytic Converters
EGR Systems

Can a bad EGR valve cause a catalytic converter to fail?

Short answer: YES!

Longer answer: The EGR valve is designed to recirculate some exhaust gas into the intake, in order to cool combustion temperatures somewhat. If the combustion temps exceed 1100 degrees (actually common in gasoline engines) then oxides of nitrogen are produced. these gases are what we see as visible smog. If the EGR valve fails, it can lead to very high exhaust temps which can gradually melt the insides of the catalytic converter. If a failed EGR is combined with a lean fuel mixture, or over-advanced ignition timing, the melting of the converter happens very quickly.

Cars & Vehicles
Emissions and Exhaust Systems

How do you remove soot from a chrome tailpipe?

A product called wenol metal polish works very well for just this thing. It can also remove rust spots as well to a degree. Make sure to clean it well with soap and water first and use a thick terry cloth towel, as you can scratch the surface otherwise. <a href="http://www.wenol.com/">wenol homepage</a>

Emissions and Exhaust Systems
EGR Systems
Dodge Stratus

How do you replace or clean an EGR valve on a 1997 Dodge Stratus 2.0 liter?

you should find the egr in the front of the motor under the throlltle , two screws hold it in place , small hands and a univeral and off it comes . to find what yours looks like you can search eBay and see a pix or in your browser type in egr and engine size . it was harder to get to egr then anything no need to remove housing , if on AOL email me and i can offer a mechanic offering free repair advice and he helped us. be sure to clean port behind egr with ice pick and vaccumm it will or maybe blocked with black carbon build up . we used a wrech and it had a twisting ten mm ? on it and used an extention on it to gain access to it. we did remove air intake and one hose for ease

Emissions and Exhaust Systems
EGR Systems
Ford Explorer

How do you remove the emissions systems from your vehicle?

Consider this a warning to anyone who is considering doing this!

In the US it is a Federal offense to remove any part of the emissions system!

If you are caught, as the vehicle's owner, you could face as much as $10,000 in fines.

AND anyone who does the work or helps (i.e. the mechanic, a friend, whoever) also faces up to $10,000 in fines.

Please be aware that there is ALSO a $10,000 reward for anyone who turns in someone who has removed or altered an emissions system - owner or mechanic.

Even if you live in an area where emissions testing is not required, you are not exempt from this regulation and you will still run the risk of being caught.

That is an awfully steep fine, IMO. I'd think twice before proceeding.

In any case you could at least check into the laws regarding this, in case the data I was given was wrong. But I had an ASE Master Technician tell me this! It's part of his job to stay on top of Federal and local regs.

If you want to repair your own emissions system, be careful and consider this first: Unless you can weld, and weld well, go ahead and let a professional do anything that has to do with the emissions/exhaust system. While it is possible to go to autozone and buy your own catalytic converter etc and put it on, it takes a lot of time unless you have the entire system in one piece. I recently replaced my exhaust from the catalytic converter back (the converter was still good), it passed but I had to piece together a exhaust system and it was the biggest ordeal ever. Stay away from Exhaust repairs if you can help it. They are tough!

Auto Parts and Repairs
Emissions and Exhaust Systems
Oil and Oil Filters
Mufflers and Tailpipes

What might cause white smoke from the exhaust after having a head gasket repair done?

Having a CRACKED head will make WHITE smoke IF U didn't have the head MAGNA-FLUXED. White smoke is steam. if it doesnt quit after awhile Id say that there is a leak in the head gasket between one of the coolent passages and a cylinder. this will let water into the cylinder which is turned into steam during combustion then exausted out the tail pipe. just to clear up something: Magnafluxing will not prevent cracks, it is a process used to detect them. This should be done by a machine shop. the new gasket is obviously faulty, or the head is cracked. I would guess that its the gasket. The head may not have been torqued properly. Follow a Chiltons or similar repair manual very closely when installing a head. If this is immediately after getting it fixed, you have to give it some time to work all that coolant out of the exhaust system. If it still is blowing steam after a few miles, then probably you have another blown headgasket or a cracked head that should have been addressed on the first head gasket replacement. Some shops have been known to not verify that the head isn't warped or cracked, and if it is, the new head gasket will blow immediately. If you had it at a shop the first time, take it back to them and have them fix it right this time - remember, though, not all mechanics are created equal and if they don't make things right you should take this to a better shop. A good shop will be embarassed by such a rookie mistake and take care of you. It is also possible that the head is warped (repair by machining) or that the intake gasket is or was also leaking or warped. Warpage typically only occurs if serious overheating occurred or sometimes if the wrong torque sequence was used during installation.


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