94 Camaro LT1 A4 Motor is stock. 163,400 miles. I had not driven it in a while (at least 3 months)

It starts up, but after a variable amount of time (roughly 1-5 minutes) it dies. Generally after it dies, it will not start back up for a while.

I hooked up a Fuel pressure gauge, and key on engine off it reads 40 psi,


Key on engine on, it reads 39 psi at idle


Key on engine on at idle with vacuum hose to FPR disconnected, it reads 43 psi


So, I think the fuel pressure is okay.

I have scanned (and csv logged) the PCM, and there are no codes logged. The engine does generally run long enough to go into closed loop. I have verified that with FreeScan that it does go into closed loop.

I do have a CSV file log that includes the engine stalling while idling. If anyone is willing to try to look at the data, I would appreciate the help.

Since it starts and runs for a while, I think I am getting Fuel, Spark and compression.

Any advice or suggestions are appreciated.

Thank you,
Steve

 

Check and see what you don't have once it dies. Check power to the fuel pump, spark at the plugs, trace backways if none there. I'm gunna take a stab in the dark and say Ignition Control Module though.

 

While the fuel pressure at the time it is running good is indeed ok. What is the pressure when the engine dies?

Since it is fairly consistent that it runs good until it warms up. We would have to assume that something electrical is breaking down after it gets up to temperature.

Agreed that checking spark is the first thing to look at. You can use a timing light as an indicator to watch spark as the engine is running and then dying. I would start at the coil wire that goes to the opti and look for an indication of a changing spark pattern.

Another method to find the "bad guy" is to use a blow dryer. While the engine is dead cold, warm one device at a time to the point it is just slightly too hot to touch. Then crank it up. If it runs good, shut it down quickly so to not get other devices warm and then move the blow dryer to the next item. As mentioned above, the ICM is one device, the coil is another and the distributor is another. However, if it were the low voltage feedback side of the opti, you would expect a code for that.

Incidentally, it would be a good idea to check all the connections between the PCM and the ignition system and the ones in between devices. I mean actually pulling them apart and inspecting the contacts of both the female and male sides.

It also might be a good idea to rule out PCM control in closed loop by disconnecting one of the O2s and let it run. If it dies then, you know it's not to do with closed loop control.