Here are the best 10 answers1
My P0300 code has been determined to be caused by low compression in 2 cylinders: due to burnt valves. 2
I had this same problem. I ended up having a new cat put on along with an engine modual and 3 coils!!! It is a lot cheaper to take it the shop trust me!!! I learned a very important (expensive) lesson...300 dollars for everything! Cat coils and engine module were under warranty on my 99 Pontiac firebird good thing I purchased that extended warranty! 3
I have a '97 Chevy Venture with the p300 code and am a serious do-it-yourselfer. I changed the obvious plugs, wires, fuel filter, and checked the obvious fuel pressure coil primary and secondary pulled the injectors and looked at them and checked them.Knowing this wasnt the problem i still checked. But I suspected a blown headgasket in between the cylinders wich "wont cause overheating" for the real novioces. well wanting to confirm this i took it to the dealer for conformation and my advise don't take it. They told me everything under the sun was causing it so lets replace one thing at a time. Well my point is this code can be a little nightmare so check cylinder pressure with a gauge before spending lots of money and keep your calm. 4
Well i finally took it in to have a new engine put in i said screw the head gasket cause the motor had to come out anyway and had 175000 on the odometer so it was probly on its way out anyway and walla' my random misfire is gone and the thing runs like a top total bill 2600 dollars with a 3yr unlimited warranty by 4star engine i figured it was the head gasket or it may even have been leaking valves but its fixed and no new car payments for years to come. Sucked coming up with the money but it made sense to me since the van was in great shape. 5
well,i have i 96 camaro v-6--5 speed--i have had a baaaaad skip for quite a while --and since i am a do it myselfer--no way was i taking it to the shop.first put in new plugs and plug wires--if it is still skipping--by that i mean sluggish runs like on 4 cylinders--your check engine light is probably on--if your car is distributorless---(no distributor)-------it should have 3(6 Cyl.) coil packs --notice one end of spark plug wire goes to the spark plug and the other end goes to the coil pack--(one coil pack for 2 cylinders)--for my camaro--they were like 21.00 dollars each at autozone--replace all of them --it is very easy --unplug the spark plug wires from them one at a time---use some masking tape wrap around each plug wire with the number that corresponds to it on your coil pack--that way you put the wires back in the right order--draw a diagram also--just to be safe--(when you buy your new coil pack it wont have any numbers cause they are all the same part just put your wires back like they were--this is a must--to change the coil packs --it is just 2 screws--take them out pull up on the coil pack--and put the new one down and screw them down---i bet this will fix your problem 6
My '97 Firebird had a code 300 for years. The SES light would come on and off, on and off for days at a time. Everyone said it was all my performance modifications and the "Hot Cam" making it come on. It turned out I had a defective computer all this time. Changed computers- problem fixed thanks to PCMforless! 7
I had P0300 code on my 97 Camaro Z28 AFTER replacing ignition wires and found it was caused by damaged ignition wires due to incorrect routing of the wires themselves. There are two areas where the wires can be damaged very easily. One is where the wires go behind the alternator bracket on the passenger side of the engine. I had completely removed my alternator bracket to replace the spark plugs (they are NOT easy on the LT1). When I routed the new ignition wires I was in a hurry and didnt make sure they were out of the way when I reinstalled the alternator braket. They got badly pinched and the engine only ran a few hours before I started getting misfire error codes and REALLY bad performance. The second area where damage is likely is near the exhaust manifolds due to their close proximity to the wires. I suggest getting some heavy duty ty-wraps that can handle high temperature and carefully bundling and routing all the ignition wires away from trouble areas when you are replacing wires. The factory ignition wire guides and support brackets are difficult to remove and reattach to with the engine in the car. I completely removed my wire guides and brackets and ty-wrapped the ignition wireshem to the engine block and wiring harness making SURE they were routed as far away from heat and moving parts as possible. My P0300 code is gone and the car runs great now. 8
This can be a challenging code to troubleshoot. My experience has lead to different conclusions. Like above, I have seen worn plugs, bad wires bad coil packs, bad ignition modules, bad ECMs, bad fuel injectors. Rarley a bad headgasket. The most common ones seem to be on the 3.1 engines. Take it to an independent repair shop and try a fuel injection cleaning. the fuel additives won't resolve it as they remove the waxes, but don't really clean the injectors. A professional cleaning involves disconnecting the fule pump and running the motor on this cleaner. I have seen it resolve PO300 codes, make cars run incredibly better or also do nothing. 9
replace the camshaft, The lobes are flat. 10
1999 Chev. Lumina.Could not climb a hill and lacking power and pep.Scanner reveals code PO300--Misfiring on all cylinders.Too involved to try fix my self so took it to GM dealer.My heart sank when they told me" TRACED TO EXCESSIVE EXHAUSTPRESSURE 9psi @ 2000RPM.--Needs CATALYTIC CONVERTER REPLACED."
I saw many hundreds $$$ flying out the window.
My spirits soared when the mechanic told me ' IT IS UNDER WARRANTY'.
Picked up car and NO CHARGE it was.
It seems that emmission parts are warranted for 7 years in Canadaand I guess in US.