lash wrote:OK, so I spent waaaay too much time reading this thread and due to the sheer volume of words, it's possible I didn't memorize everything that's been said.
I know you've replaced the coils and/or tested them, however...it's not uncommon for the S1s to have coil problems. More specifically, members here have had issues with the coils
upon heating up. these issues almost always show up as intermittent and bear some additional consideration. Additionally, you mention that you've had it down to the plate, but I don't recall you saying that you've tested the ICM itself. I suggest doing so if you haven't already.
Another thing that caught my attention is that you feel pretty strongly that it's and electrical problem and that may be so. Have you considered that it may be a major sensor problem. IIRC, yours has a MAP sensor.
Your major sensors, MAP, engine temp., and crankshaft position sensor can all cause the car to go into limp home mode and may cause it to run exactly like you mention. Additionally, the first two, MAP and engine temp are specifically affected by temperature.
These are cases where a scanner could very well help you to diagnose it, IMO.

Way to long. Hmmmmmm. This is a very good post. Lots to learn here. Well worth your time. I've learned a few things in it myself.
IIRC?? Is that my model??? A sensor. I've worked on so many different cars. That, I can't memorize the series numbers for all of them. It's a 93 3.8 bonneville se. Series 93. LOL. I have only put parts on it from 93 Standard Edition 3.8 GM's built in the same factory. Bonneville, Lesabre, 88. Don't believe there was a chevy. I use the vin code to identifie the year and, engine.
If, it was in limp. My SES light would be on.
It has a brand new CPS. No change.
Map sensor. Manifold Absolute Pressure. Goes rich 0 or, low vacuum. Black smoke. Fowled plugs. It's not a rich problem. Don't recall seeing one. I don't have the component locator. I'll check it out. About, all I can do is unplug/replace it. It's obviously not a vacuum problem, to it. Where's it located??? BTW. In the dash, somewhere??
I've changed many DIS coils. They cause a misfire. No Fire. Never on all cylinders. I've rotated checked coils on this car. It is like it's fuel pressure drops to like 10 lbs. No power. Backfires into the intake.
Temp sensors. Hmmmmm. How hot would it read to lean the mixture this lean. Out of parameters. SES light would come on. Besides. I've checked the resistance on it several times. Just hoping and, the whole time knowing it's a waste of time.
I have no codes. The mass airflow meter is the substition style. It looks new. And, unplugging it does not change the problem. Just sets off my SES light. It runs good cold with it unplugged, too.
I have not changed the TPS yet. Highly unlikely. But, I'm thinking about it. Easy and, cheap.
Checked the ICM. I've changed it. The ICM Mounting Plate is under the ICM. Still did it. Now, I have an extra one. And, I have a extra PCM, too.
Scanners. OK. I've used them. Don't feel a need to buy one. Since, I can read everything at the PCM with my Snap on Digital meter. I just need a good wiring diagram. Besides this is a ghosty intermittant problem. So, I'd have to have the scanner hooked up while it was happening. I still highly suspect power/ground missing. Does your scanner check all the grounds??? And, I'd love to have one. Cost more than I paid for the car. Besides, I've been fixing Computerized cars since long before scanners came into being. And, when they did. They were good for seeing sensors out of range. Checking injector dwell, pulling codes, ect. Some grounds could be read with the ones I used. I'ved used Sun and, Bear scopes. The bears had built in scanners. I've used snap on scanners. Sold them because of divorce. I know they've come a long way. But, I can see everything a scanner can at the PCM. I need a wiring diagram and, a ground locator.
I do have my fuel pressure gauge in the car, now. So, if it does it again, I can verifie the fuel pressure when it's acting up.
It's supposed to warm up this weekend. So, maybe it will act up.
God Bless,
Chris

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Just a long haired country boy.