2003 Chevy Impala can't accelerate... Help Please!?

It does fine when I first start it when I’m climbing up to 35 mph, after a while, especially as the day goes on and it gets hotter, it has trouble accelerating… It sounds like it’s grinding… once it passes 65 it’s fine… The air conditioner also died… My mechanic can’t find what’s wrong; he says the transmission and the gas systems are fine; he hooked it up to that machine but the machine says the car is fine. At times when I’m stepping on the gas trying to get it to go, the check engine like turns on and stays steady, but next time I drive the car, it’s off. It is due for an oil change and the change oil lights up, but my mechanic saw that and he didn’t mention that was it… Please help… anyone!!! This morning the check engine light stayed on and I had trouble accelerating from the start.



I’m thinking of trading it in even though I know i’ll have negative equity w/ the trade in. =(

I don’t understand how your mechanic can find no codes when the CEL is on.

Drop by a local AutoZone, Advance, Checkers, etc., whichever one is near you, and have them pull the codes. Post the results back here for further discussion.
These places will perform this service for you absolutely free and sometimes an outside opinion, if you want to call it that, may be better.