Chasing an Engine Misfire... any input

[speedfreakcl]

Ok, so i have a 91 sunbird that originally came with 2.0L and swaped it out for a 3.1L and manual trans...

was running great and then i started to have an engine miss first diagnosed was injector failure.. tested all injectors and replaced the faulty injectors..

Because there was injector failure the computer was giving a code 43 which is an ESC (Electronic Spark Controle) Meaning the computer was retartding the spark to have the engine run a little better due to the miss. cleared the code but didnt fix the problem...

Still giving a code 43... Replaced the ignition module.. didnt fix it... replaced all three coils and all plugs and plug wires... didnt fix it..

now not only am i getting a code 43 im also getting a code 13.. O2 sensor failure...

does anyone have any suggestions as to why i continue to have these problems or have encountered something similar and what they did to fix the problem...

[Spyder3K]

Hey, when you did all of this, did you reset the computers in the car? (I.E. disconnect the battery for 30 min of duration)

[J-Ri]

Check the O2 sensor output with an oscilliscope if you have one, otherwise just replace it, but use a GM part. I've seen cheap O2 sensors that were worse than the one they replaced. It could be as easy as the O2 sensor making it run lean or rich and causing a misfire. What year is the engine/PCM?

[speedfreakcl]

I have disconnected the battery to clear the codes and did an idle learn on the car due to it being a manual trans, idle was really low began to stall when i would come to a stop and or just idling...

I am going to replace the O2 sensor tomorrow and have another idle learn done hopefully Monday if i can find some time to do so...

Im hoping it is just the O2 sensor thats needing to be replaced.

The engine and trans and PCM were out of a 1992 Z-24 cavalier, if the PCM had been changed prior to me taking ownership of the car I couldnt tell you.. Is there any way to find out what year the PCM is??

[speedfreakcl]

Ok so i have replaced the O2 sensor, have not done an idle learn on it as of yet but already the check engine light has come on....

The car runs smooth and then once it gets to a regular operating temperature i will hear the engine idle change and count to 3 and the check engine light will come on...
by the change in the idle i can tell that the code that will come up will be a code 43.... again.... and because of this code it could cause an O2 sensor failure down the way cause its running to rich or lean...

So i have in the last 3 months replaced all three coil packs, the electronic spark controle module, the plug wires and plugs.. all good quality parts and im still having a problem.
The only thing left would either be the remote wire that goes from the module to the computer is grounding out and causing it to do soo, i dont think its thats...
But it could quite possibly be a computer failure..

Has anyone ever had a similar problem and what else could i check... before going and replacing the computer...

[Jason/RKBA]

Have the ECM tested. Also it could be the EGR valve and or solinoid holding the valve open while ideling.

[Aaron_0703]

SPARK PLUGS!!! i had the same problem check those an the cables/boots... or it can be a problem with the fuel injection mite need new ones.... or it could be even ur vaules are all burnt out...

[J-Ri]

It's got to be something electrical, a mechanical problem would do it all the time.

One last thing I would check before throwing a PCM at it is the knock sensors. If they're showing the engine knocking (even if it's not), the PCM will retard the timing. I also remember something about the knock sensor setting a EST code, or disabling it or something. I wouldn't count on that being it, but it's somethign else the check

[speedfreakcl]

Thank you everyone for your input... and helpful ideas to check... I have found the problem and that was... the knock sensor... every time the car would heat up to operating tempurature the heat affected the knock sensor and caused it to fail...

so now my car it working and running properly... no check engine lights anymore finaly

Thanks again
Craig

[J-Ri]

No problem, glad to help.

And thank you for posting the fix!