mudgod2@yahoo.com

Have a 92 lt-1 and when it fires up, runs perfect for a few minutes then when it starts to warm up it will run rich, miss and seem to have no power at idle. When i rev it up runs ok at high rpm. Both o2 sensors are good and it doesnt pull any codes. Please dont tell me the opti. I have had a delteq ignition sysyem on it for 2 years and have had no problems, just installed this motor and trans from another car. Ran fine then, was hoping maybe a sensor somewhere, just replaced the coolant temp sensor on the front of engine,(broke the old one on engine install). Seemed to help a little but something else is wrong. Anyone?

racebum

what you're describing is a problem somewhere in the ignition cycle. either timing or spark. i honestly have never diagnosed an opti car but your symptoms are universal with 4 cycle engines.

ex-x-fire

Did the replacment engine come complete? Maybe has mods, big injectors or hot cam.

-=Tom=-

How do you know the O2 sensors are good? That sounds exactly like a bad O2 sensor since they're out of the loop for the first few minutes while the car warms up.

I had a similar issue a little while back. It ran fine at cold starts, then ran rough after it warmed up. No codes either. I hooked up my laptop and watched the O2 sensors while the car was running and could see the driver's side reporting low/whacked out numbers. I replaced that O2 even though it was only 2 years old at the time and that rectified the issue.

Good luck with trying to diagnose your issue. Let us know how it turns out.

0Paul Ruggeri

You need to see the actual readings from the sensors and know what they're suppose to look like. Try to find someone knowledgable with a scantool.

SunCr

Assuming it's stock, clamp off the air hoses to the headers. If it goes away, the air pump probably isn't shutting off or a check valve is broken.