93 Cherolet Lumina backfireing help

[shortie66112]

I have a 1993 Lumina that keeps making a popping sound in engine when I accelerate. Have had a friend say it is backfireing in the breather and might be out of time. I have a 3.1 engine. Someone please help me

[jeffcoslacker]

If you have intake backfire on acceleration, that's an indication of an overly lean (not enough fuel) condition in one or more cylinders. The timing is non-adjustable on yours and if the timing were off enough to cause backfire (say from a slipped timing chain or something) it would most likely be undriveable.

My guess would be you are looking for a fuel delivery or mixture control problem, perhaps a faulty injector, MAP sensor, fuel pump or pressure regulator, etc.

A large vacuum leak that feeds one cylinder can cause it too, sometimes. But that would generally cause a very poor idle, either way too high, or very unstable and shaky, depending how the engine management system sensed it. Since you didn't say anything about idle quality, I assume this probably isn't an issue here.

How many miles on this car?

A momentary loss of timing signal could probably cause an intermittant backfire, like if the Crank Position Sensor's signal were breaking up, but since it is on acceleration consistantly, I doubt this has anything to do with it either.

When you press down on the throttle, you suddenly admit a large volume of air into the motor. The management system has to see this before it reaches the cylinders, and signal the injection system to increase fuel delivery to match this incoming charge of air before it gets there, or else the overly lean mix will detonate from the heat in the cylinder before the intake valves close, and voila!, popping backfire through the intake.

A broken or otherwise damaged intake valve will cause this too, but in a continuous series of small sequential backfires as long as the throttle is demanding the motor to labor.

Is this the case, or do you just have one or a few random pops or woofs as it accelerates?

[shortie66112]

it has 135671 miles

[comptech_69]

I've only had my car backfire when It was running out of gas...

....Although it also backfired when I had a bad coil also.