is this just a vacuum problem? I hope so

[Goph]

I'm out driving for like 30 minutes then i get home let the car cool down some and shut it off. I go back out in like 10 min. and start it back up and it start shaking and the RPMs are going up and down a lot then it go up to 2k rpm then slowly down to 1k.

 

This is in my GP with a rebuilt engine with less then 250 miles on it. I had the vacuum modulator replace when the engine was because of a tranny problem.

[Guest Anonymous]

Check your IAC valve. Sounds like it isn't resetting itself.