I have a '99 Sunfire with a 2.4L that I just had rebuilt. Now the Engine shakes like crazy and I had new Engine mounts put in so I know its not that. Can someone please give me some advise to what the problem could be.

what kind of shake? rattle? or violently shakes or what? i dunno the inner workings of the engine, but i have heard if the crank is improperly balanced it could cause that.

im with Tuner here.. drop the pan and make sure everything's bolted in place and secure.. when the motor was rebuilt- did u have the crank milled at all? there are 3 mounts on that motor- are all in place and secure?

could be a map sensor or uh..... ah shit i can't think of the other one at the moment. .... Idle Air sensor. Is your tach goin all over the place. Could also be a vaccum leak. I have this same problem right now. But i just priced out the parts and they weren't pretty. So i am going to use my warrenty... ha ha...