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?
Originally Posted by BillBoost37
