Mysterious behavior

I have a 96 chevy lumina sedan that decided on christmas day to only run for twenty minutes at a time before choking out and becoming undriveable. After cool down it will run another 20 min. then repeat the whole scenario…A mechanic friend said to check the exhaust pressure at the tail pipe at start up and then when the stalling begins to check the cat. converter. I did this and there is a noticeable difference ( of course I had to be care ful not to burn my hand on the second try…) no trouble codes or any other symptoms, could this behavior be caused by a clogged convertor? Thanks.

That what it sounds like,engine can’t breath.

It’s possible the convertor is plugged and causing the problem but not likely.

When it doesn’t run is when you need to check for spark. This sounds like a defective ignition control module. When it heats up there is no spark, then when it cools down it has spark and runs.

On second thought, Willey is correct, slipped my mind on that one. It is a quicker to check that one out than to replace the catalytic converter.

Is that underneath the coils? and is that a separate part? or is it all one unit?
Also, engine will still idle, only when under load does it not run correctly…if it’s the ignition module would it still idle?


Look for the possibility of a leaking fuel pressure regulator. There is a hose that runs from the regulator to the intake manifold. Remove that hose and if fuel is inside the diaphram is leaking. If so replace the regulator.

Check the Coolant Temperature Sensor and its wiring. Is the CTS resistance dropping appropriate with the coolant temperature? Is there an open or poor connection in the positive sensor line to the sensor? If the computer always thinks the engine is cold, the mixture will be too rich when the engine is actually warm and make the car undriveable.

Come back to us with the outcome. Feedback engenders learning.

I had a similar problem with a 80 ford with the ignition module. Not to say that there’s anything wrong with yours. But there could be.

How did you determine what the problem was? Did you take it to a garage? Is there a test for it?

Check for spark getting to the plugs while the trouble is occuring.

Just for fun, try something. Next time it stalls out see if it will restart after loosening the gas cap. There have been cases of the fuel tank not venting properly, leading to fuel starvation. It’s a long shot, but it’s easy to check.

First of all, thanks to everyone for helping! After 3 hours of somewhat frustrated searching, I found the culprit (Pretty sure)…2 wires leading from the IGNITION MODULE had somehow melted against the exhaust manifold!!! I pulled them off and retaped them…took the car for a ride…and everything seems fine…another mystery solved! Thanks again!!!