Car will not shift up after 2nd gear

I'll let you know when I check my car out. I've had it for about 5 years now and it just started to do the same thing. My brother in-law is a heavy duty mechanic and he doesn't think it's the transmission, but doesn't have a computer to check for errors. I've read all kinds of things, like manifolds, loose plugs, and several other wires that may be disconnecting. So there is hope for both of us that it is an easy fix rather than an expensive one.

Good Luck!

I took it to a trans shop. Of course they said I need a new trans and misc stuff adding up to $2800. I said screw it, I will do it. I got the car back and drove ten miles. It started doing the same thing! I heard a loud bang right by my foot. Must be the trans, I thought. I took it back and they tested it and have not found anything. It also did not show the same symptoms after 50 miles of them driving. So I dont know! I'm going to drive it until I wreck the trans and make them fix it under warranty.

I know its been a while but did you ever figure out anything with your pontiac sunfire? Mine will not shift out of 2nd. I ve read a lot of forums and it seems to be somewhat common but no one ever comes back and tells what fixes it.