the seat on the exhaust valve is dirty so the valve does not seal it.... not sure how to clean it
i think the computer need to be reprogram
if it only backfires when shutting off, usually this means its getting to much gas!! if it backfires will running adjust carburater.
Most O2 sensors are in the Exhaust pipe running from the back of the manifold. It is silver with a single black wire running to it. It threads into the exhaust pipe like a spark plug and can usually be accessed from under the hood. Happy Wrenching.
If it runs, it will miss slightly and RPM gauge will be lower than the 800 RPM normal. It could exhibit some "thumping" sounds at the exhaust which is exhaust being pulled back because valves are not properly closing - test this by holding a piece of paper at exhaust and see if it pulls back into pipe instead of constantly blows away. If it backfires while starting or running.
If any car backfires it is usually due to retarded timing, running lean or a problem in the valve train.
running lean can cause your 400ex to backfire ..if it backfires on deceleration its lean ...if it pops on acceleration its running rich.====carb issues
missfiring cylinder possibly due to fouled spark plug, ignition timing incorrect (leads swapped around). The reason for the backfire is unburnt fuel accumulates in the very hot exhaust system and ignites there.Or...If the engine is running and did not previously back fire, and now backfires when the throttle is rolled off (on the over-run) then the most likely cause is an air leak either in the inlet manifold, between the carburettor and the head, or in the exhaust system, often where the pipe joins to the engine, or where the silencer joins the pipe.These backfires are due to a LEAN mixture failing to ignite properly on every cycle and so allowing unburned fuel to build up until it finally goes 'bang'if it backfires but won't run at all, then it could be several things from the camshaft being 180 degrees out to the spark plug leads (on a twin or multi-cyclinder) being on the wrong plugs.backfires occur when not all the fuel is ignited in the engine and instead ignites in the exhaust.
Day time running lights?
Needs a tune up? Bad timing?
No, I recommend go to a mechanic, chances are your firing order is out or running bit to much fuel
have a pontiac 6000 2.5 motor and it wont stay running
It's a turbine mounted in the exhaust manifold to give more power and smoother running to the engine.
Exhaust system backfires occur in engines that have an emission system malfunction, like an air injection system diverter valve problem, an exhaust leak, or when the catalytic converter has been removed. In some high-performance vehicles, when a driver shifts up and lets off the accelerator, the engine has a moment of running rich. This causes an incomplete burn which causes the fumes to explode in the exhaust system along with an audible clacking sound. However this condition is a result of working smog equipment, and is unlikely to cause any damage.A fuel injected engine may backfire if an intake leak is present (causing the engine to run lean), or a fuel injection component such as an air-flow sensor is defective.Common causes of backfires are:Poor or unregulated engine timing is often a cause of intake backfires, but can also be responsible for exhaust backfiresImproper wiring in the ignition can also lead to timing issues and backfiresLow fuel pressure, clogged fuel filters, and weak fuel pumps could cause a severe lean air-to-fuel ratio during fuel injectionMissing or damaged catalytic converter can result in backfires out the tailpipeCourtesy of: WikiI dont know that much about cars, but when my friends Mustang backfired, there was a timing issue in his engine which also affected his speedometer! But his car is a 1980! LOL! So I would get it looked at!
because of the exhaust
You can expect your engine to vibrate some. Other than the visible vibration, is the engine running smoothly? No missing or backfires or anything like that? Excessive vibration might be due to faulty motor mounts or missing hardware at the motor mounts.
Engine is running lean.
I dirt track race and mine did it once it was because it was running to lean.
white exhaust and rough running usually indicate possible blown head gasket.
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If it backfires after you shut it off then it is probably running too rich. Any unburned gas the that is exhausted out and into the muffler will explode with a backfire. With a 1990 model you won't have the anti-backfire solenoid on the bottom of the carb like the newer ones have. If it backfires while it is running it might be out of time. Check the keyway between the crank and flywheel to make sure it is not partially sheared.
Are you trying to remove the exhaust manifold,the muffler,or just the line running from the manifold connection to the muffler?
Moisture in the exhaust, or a cold running engine.