Rough idle and Engine Light

[Manakin]

Ok I couldn't get any spark from my 81 .I replaced the Ignition module and coil.It still wouldn't start.I just replaced my ECM and voila it started.Now I have a really rough idle and when I give it gas it sputters.If I give it alot of gas the RPM drops to zero then backfires when I let off the gas.What could the problem be.The check engine light is on as well and smoke coming from exhaust.

 

[GerryLP]

Ok I couldn't get any spark from my 81 .I replaced the Ignition module and coil.It still wouldn't start.I just replaced my ECM and voila it started.Now I have a really rough idle and when I give it gas it sputters.If I give it alot of gas the RPM drops to zero then backfires when I let off the gas.What could the problem be.The check engine light is on as well and smoke coming from exhaust.

With those weird and off the left field problems (like the vette is running fine, but then acts up all of a sudden), I always recommend to reboot the computer by disconnecting the battery for about 5 minutes. When you reconnect the battery, the computer takes a new set of values.

If it continues after that, then search for loose vacuum and electrical connectors. After that look for leaks between the intake manifold and the heads or the base of the carburetor and the intake (spray some WD-40, and if the rough idle goes away or the rpm increases, then that's the culprit). Just remember that you could have a dual leak situation. Also, look at the oxygen sensor cable to make sure it did not come in contact with the exhaust.

 

[82ColEd]

Are there any codes that you can read out, maybe that'll give a hint as to where the issue is.



-Stefan