Backfiring when Accelerating, but not when revving in Nuetral or at Idle. What could this be?

Could it be because the car needs tuned? If the PCM was tuned and the battery was removed, would this cause you to lose whatever tuning the car had received in the past?

I have replaced the coil and ICM recently. Along with the distributor, wires, plugs, etc.

Does this seem like a tuning problem or maybe the MAF or ICM?

 

It would be useful to add a "Signature" - basic info like year, model, engine, trans an any major mods. I think in your other post you had a 96 Z28, and listed your mods. Put all that info in your signature. Because of subtle differences in the LT1 from year to year, it helps people help you.

 

Thanks for the tip...

 

Does your SES light flash, indicating a misfire?

Have you had it scanned for codes?

When you say "backfire", do you mean the combustion is backfiring through the intake manifold, or the exhaust is backfiring?

The PCM "tune" (program) is stored in non-volatile memory. Pulling power to the PCM will only clear the volatile memory (long term fuel corrections, most stored codes, learned IAC position). It will not alter or delete the program, which is what gets modified when the PCM is "tuned".

 

Yes the SES light is on. It has been and the codes that are present are the following.

something about the mass airflow sensor
Something about shift sensor
some sensor on the gas tank.

 

You need to get the specific codes. There are four different codes for the mass air (MAF) sensor. One indicates it isn't working, another indicates its working but the flow numbers are not rational, two more indicate the flow numbers are outside the normal range. The first one could indicate a faulty MAF sensor or a faulty 12V power supply to the sensor. Irrational flow numbers may indicate the sensor is dirty, or the rubber elbow between the MAF sensor and the throttle body is torn.

I'll bet the code for the "shift sensor" is for the skip shift solenoid? Have you defeated the skip shift system? This code isn't going to cause an engine problem. P1657?

There is a pressure sensor in the gas tank. Have you checked to make sure your gs cap is on tight?

 

I will run back to Advance and get the specific code it is throwing on the MAF.

I have tightened the gas cap, but that could have been why it was throwing the code.

I think shift skip was the term I heard, I wasnt real concerned about it. I honestly wasnt concerned about the MAF in the beginning.

Back to your question earlier. I dont know if the backfire is intake or exhaust. I have straight headers at them moment and I just cant tell.

 

Removing the battery will not cause the program to be lost. The fuel trims will reset, but that is no big deal. The PCM will "relearn" them quickly.

What parts did you use in the rebuild? What brand of optical distributor, ICM, etc? Were the rockers touched in any way?

Do be sure and do as Injuneer suggested.

 

They(The person I purchased car from) used a BWD Distributor Cap and rotor kit, with a Cardone distributor.. Its the Advance Autoparts special I guess. That was done the week I bought the car. I put a melling standard volume oil pump along with a new drive shaft and drive gear. Thats all that was added while the car was apart. Everything looked great in the engine.

I did have a rocker arm stud broken and when I turned the engine over a lifter fell out. The lifter must have been kicked somewhere because it was lost. So, I put a new lifter in the car with a new rocker arm stud. I didnt notice any more problems.

 

Anything other than a brand new AC Delco unit for the opti spark is generally a mistake.

Are you absolutely sure that the plug wires are on the correct cylinders? No damage to the wires either?

 

If you are running open headers??? That can cause the O2 sensor to read incorrect. Try putting some pipes on there and see if it helps any.

 

I filled her up with new gas and added some octane boost. seems to have helped for now.