90 runs / stops after 10min no spark

I need a fresh look at this problem. 90 Euro 3.1 Runs like a dream. Motor and tranny were swapped out of 89 Old Cutlass Sup. last summer. Has run very well. Recently the car died on my wife on the hiway. No spark. Checked to see if fuel in fuel rail. And fuel came out of relief valve.
Changed Mod. and coil pack. Run fine for 5min. No spark again. Changed Computer. Run for 7min. No spark. Check for codes. No codes. Wait for 10 min and car starts and runs fine for 20min than dies. When the motor dies it just stops. Since Ive had this problem. It seems to stall out like she is flooding like with a carb. motor. If I happened to be in the cab when it does this I just give it gas and it comes out and run fine.????????????
Had my mech friend look at it last night with his Scanner couldn’t find any thing running out of spec. IM looking at other posting of similar problem for some possible clue as to what maybe happening. Any help or fresh ideas may send me in the right direction.

could be one or more of your fuel injectors. that 3.1L is known for the injectors overheating and burning up. you can use a OHM meter to check them should be between 12and 14 ohms. you can also take them in to have them flow tested to make sure the switch inside is working correctly.

it is probally the crank sensor. when it is going bad it will shut your spark of after warming up , usually takes 15 to 20 minutes. it costs about 30 for the part. and is located behind your harmonic dampener.

it is probally the crank sensor. when it is going bad it will shut your spark of after warming up , usually takes 15 to 20 minutes. it costs about 30 for the part. and is located behind your harmonic dampener.

Yes. I'm liking the crank sensor on this one, too.