I have a 99 Dakota 3.9 4wd. When I stop with the truck in drive, it idles at around 750 rpm's. Then if I shift to reverse, neutral or park, the rpm's drop off to around 500 and it trys to stall. Then the rpm's go up to around 1000 and then drops back to 750 and all is fine. Any thoughts?

 

i would look to see if you have a vacuum leak, if not clean or change your IAC.

 

Thanks, I'll start there.

 

Any common areas to look for vac leaks?

 

i have the same issue. i replaced the AIC and the TPS, ran sea foam in the tank, checked for vacum leaks... if u figure this out let me know what u did.

 

Could also be the plenum gasket.

 

look down the tb for oil to check that