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Having tranny problems but it could be something else...

C

Calikid219

New member
I have a 1997 Pontiac Grand Prix with 187,000 miles and the original 3800 but I got the transmission replaced with a rebuilt/refurbished because the old one was slipping alot. Now, about 5,000 miles after getting the rebuilt transmission installed, every time the car is put under pressure (about two bars of boost on the boost gauge) the car starts hesitating and the loss of power is very evident. When the SES light comes on (which it doesn't every time), it reads as a cylinder 1 misfire. My dad and I thought that the transmission was only having trouble downshifting out of overdrive, but this problem happens in whatever gear it's in, even first. On the contrary, if you're cruising along at say 65mph and you let your foot off the gas, then step back on the gas, the car will downshift depending on how hard you step on the gas, like it should. So, it can downshift, just not on its own. There has to be some sort of human interaction in order to make it downshift. It all seems like a transmission problem except for the fact that it hesitates in first gear. Why would it be trying to downshift from first gear? Anyway, we thought it was a transmission problem but now we're not quite sure. Any guesses?
 


The car is very well maintained as my dad and I are car guys. The plugs were last changed 4 years ago but we haven't touched the maf in quite a while.
 
If you get a misfire code.. there might be other underlying issues that are keeping the pcm from downshifting based on power etc.
 


Out of a 100 times I hear/see people say could be an ICM.. I think it's been less than 1% that have been fixed by an icm
 
I've had a no start be fixed by an ICM twice recently.. and one misfire/bizarre KR issue ended up being an ICM.. but usually ICMs are not the issue.
 
When you changed the plugs, did you install stock irridiums? When was the last time wires were changed? If it's been a while fire it up in the dark and mist some water over the plug wires and see if you get a light show. If you do, then the wires are leaking voltage. If you still have the stock metal plug wire heat shields on I would junk those too, they're not needed.

Would also be a good time to remove and clean the MAF with approved MAF cleaner (don't use brake/card cleaner).
 
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