Hi Folks,

I'm stranded in Ft. Wayne Indiana and I need to find a good mechanic. I've got a high speed stumble only when the engine is hot. For now I'm not asking for input on what'* wrong with the car because I've gotten good help on another forum with that already. Spent the day today in a pretty good, shop, but this problem is really a tough one to solve. Everything is scanning out fine, and I need to find someone who is really good.

thanks in advance

Any more information you can give us?

Is it only when accelerating? My first thought is a bad coil pack or spark plug.

Got a check engine light? Have you gotten the car scanned to see if it has any codes?

Hi, thanks for the reply, I appreciate it. Please don't take this the wrong way, but what I need right now and asked for was a recommendation for a mechanic. Every possible cause has been scanned and analyzed on another forum (pontiacbonneville.com) ad nauseum. I had problems with stumbles when the car is hot for a year now, and have repaired and replaced lots of stuff that solves the problem for a while, then something else pops up as a cause. The mechanic today was good and scanned the hell out of it. Many parts have been replaced already, including the ones you asked about.

No, it'* not just when accelerating. I'll be going along at, say, 70, runs fine for a half hour, then starts to stumble and miss. I slow to 60, runs fine for 5 minutes, stumbles again, etc. If I let it sit for 10 minutes it will run good for while then it starts stumbling again.

Plugs and wires are new, and the car was scanned today. No codes or CELs

Coil packs check out good, new fuel filter, crank angle sensor, main engine computer...

fuel pressure is good, even when checked during stumble mode.

Ah, guess I didn't read through your post well enough. Wish I could recommend someone to you but I'm not familiar with that area.

We do have a couple Guru'* on this forum though if you are still willing to accept some advice. Perhaps send a PM to billboost37 or danthurs. Both of those guys have quite a bit of experience in the realm of the 3800 and I'd take their advice over a mechanic any day.

I value the gurus very much and have read everything they and everyone else has written about hot stumbles in 3800s in this forum and others over the last year. The idle air control valve was replaced today after 2 hours of diagnosing, because a scan showed it was malfunctioning while the engine was stumbling. They thought that was the problem, so I paid, and headed home, and then it started up again 10 miles down the road so I turned around and came back and will return there tomorrow for a better diagnosis or my money back for today'* work.

Take a look here and see if this is related.
https://www.gmforum.com/showthread.php?t=278980

Thanks, I may check that out. if that were the problem why would it only have an effect when the engine is hot though?

The wiring at that connection gets hot. The corrosion increases in resistance and causes the fuel pump to either not work at all or slow down.

I only based this idea because of your location in the Norther States. Most southern vehicles should not experience this problem at all. It happens to Northerners because of snow and salt getting tracked into the drivers side compartment.

Do your power windows/locks seem difficult when this is happening. It all shares the same ground.