[QUOTE=BALLSS;993491]Your FP looks to be holding. BTW the FPR is what keeps the pressure right with a good FP
Your stumble may be ignition related. Either Opti, coil or ICM. Unless any codes are being thrown, very hard to diagnose a Opti without a Oscilloscope. If Opti is not a AC Delco or Delphi that the off brand ones are highly suspect. Failing ICM can cause stumble but typically the are a no start or once car warms up engine shuts off and won't re-start...although I have had them just make the motor barely run but will start.
If your issue starts once car is warmed up....replace ICM
Do you have EGR on?
If so reach around back of it with engine running and push in the diaphragm. The engine should stumble, maybe stall. Does it?
Thank you for your responses. My plan is to purchase an Oscilloscope and learn how to use it. I have never worked on a car that is run by a computer. My last car was a 1939 ford flathead so I have about 60 years of automotive technology to catch up on.
The issue with the stumbling begins almost immediately so perhaps the cause is not a bad ICM.
I have tried to check all the vacuum lines and hoses and I have not noticed any leaks.
I do not know what EGR is. I can not locate that in my Haynes repair manual. Could you please explain? I will then perform the test that you have suggested.
I have a notion to just purchase new ones of the coil and distributor and replace what's on the engine now. My hunch is that would solve the problem. However, I would feel much more satisfied if I can solve this with a proper diagnosis procedure including the use of the Oscilloscope.
Despite not being able to fix the problem yet, I am enjoying the diagnosis process so far. and I am learning a great deal about my LT1 engine.