Well - back from vacation - back to the car - symptoms are that engine drops out and dies when up to temperature - runs perfect open loop while cold.

Had some correspondence with "388 solid roller" having the same or similar problem. After checking all connectors - Opti, ECM, coil, ignition module - decided to do some running tests. All tests were done with the car idling in the driveway - 1 hour wait between tests in order to let her cool completely. In all tests no trouble codes were thrown by the ECM.

1) Checked fuel pressure - builds to 43psi backs off to 41 psi with pump on - with engine running, pressure steady at 39 psi up until she dies - no change during event - this appears A-OK! Car engine died after 10 minutes idling.

2) Replaced ignition coil on theory it might open when hot - car ran at idle for about 10 minutes before dying - water temp 205° - oil temp 145°.

3) Went through troubleshooting flow charts for ignition system per Haynes manual and GM service manual - seemed to indicate either ECM or ignition coil driver module. Bought ignition module for $68 at Advance Auto Parts (part #EL151 - GP Sorenson lifetime warranty part). Tried running from cold condition - ran 10 minutes until it died again - this time water temp 210° - oil temp 155°.

All I can figure now is that the signal from the ECM is not there when she warms up -

Weird thing though - on all test attempts, the fans DO NOT kick in for cooling, but when it dies, if I cycle the ignition key off and then back to on, it kicks in. Is there a symptom connection here? Hmmm.

End result - looks like the ECM and the Opti are the last items to go over - I replaced the Opti with the 1995-1996 modified unit last fall (less than 500 miles on it) - visual inspection shows everything to be in order - no traces of moisture or anything else on the cover.

Who has the best price on a new or rebuilt ECM - figure that's next in the loop. Any other suggestions anyone might have is appreciated!!

Will post again after Round 4!!

:mad :confused: :mad

 

I have a 96, but everytime my car has the symtoms you describe, it's an intermittant connection to the coolant sensor (on the front of the H2O pump). I just check the sensor's reading with a scan tool as the engine warms up, if it's bad, it'll be obvious.

Eric

 

You can check the ecm coolant temp from the digital dash. Check the reading when its cold and compare it to the oil temp, then check the it when the engine is warmend up and when it dies.

This could be a connection problem at the sensor or it could be the sensor too. Check the ecm for codes too.

 

Sounds like the ECM to me. I worked on a chevy lumina that when it warmed up would sputter and die. It would run reallllllly rich. Tried lots of things, then we finally replaced the computer, much better now! :cheers:

 

Thanks for the feedback guys!

Tried her one more time tonite after recleaning and reconnecting everything - again, she ran for about 10 minutes at idle - this time oil temp 155° - water temp 218°. I've read that the ECM won't trigger the fan until 226° - the car won't run long enough to get the fan triggered - uuunnnhhh!

Assuming the Opti is good, looks like the ECM is the item of last resort - anybody know where the lowest cost source might be? I'm sure not going back to the Chevy garage here for one!

:mad :rolleyes: :mad

 

MY PROBLEM IS SOLVED!!!! I took off the ignition thingee with a heatsink, the one mounted above the coil - off and cleaned the entire piece, cleaned the mounts etc. I removed the ground wire (dont know what its for) that bolts to the block near teh coil as well and cleaned/filed it too. i put everything back together. Teh car ran for 15 minutes and stumbled, and shut off, but this time it started up again. After 10 more minutes it stumbled when the gas was pressed but i kept on pressing the gas pedal and it was fighting to shut off... it didnt . it stopped stumbling and now its fine. i dont know if cleaning everything helped or not.
Personally, im confused as to what helped. Homer, try cleaning everything and filing all the grounds to make sure they are grounded fine. I still am leaning towards it as an ecm problem in your case. I doubt it is an optispark , liek you mine is new and i ruled it out. if it starts and runs perfect for 10 minutes i doubt it is ruined. Also try and disconnect the battery when cleaning everything.
I noticed that there was coolant between the ignition module switch and the plate behind it. The back of the switch (the thing above the coil) is metal so i think it needs to be grounded to the block. not sure but it seems to have helped me out.
Maybe it will happen again ,who knows.... ill let u know if it does. good luck. :seeya :cheers:

 

:cheers: :cheers: :cheers: :cheers: :cheers:

 

Thanks for the tip, 388!

There's a good chance you're right - a bad ground might very well be behind my problem - will give it a go tomorrow (took today off from it!!) - will let you know!