Bought a 96 Monte Carlo that has sat for a while. When cranked the rpms can start off anywhere from 1500 to 3000. They start to climb almost immediately and only go down if I shut the car off and crank is back up, then they might sit around 1000 before slowing climbing back up. The MAP senor is where I'm going to look first, if I can get it off. (Found a ratcheting 10mm on the side the road, stuck it in my tool box and can't find the dang thing now.)

Is there anything else I should look at? Any special vacuum lines to check? Other sensors?

All help is appreciated.

 

Generally there's only 2 reasons RPM can climb on its own on a cable driven throttle body - something wonky going on with IAC (much less likely) or some kind of vacuum leak (much more common).

I'd start by checking for vacuum leaks after the throttle body. Waft some thick smoke into the general area of the top end of the engine and start looking to see if it's moving somewhere (degraded hose, cracked manifold, bad gasket, etc). Once you've got a feel for area, you can concentrate the smoke to try to identify the culprit.

 

Thanks, I'll see if I find anything.