I recently picked up a 2003 Venture that needed a lower intake gasket and I'm having trouble finding a solution to an odd problem. When I start the van it idles fine until I put it in reverse or drive, and then when I return to park or neutral the idle is very high. I can shut the van off and restart it and it's fine until I put it in gear again. This problem was there before changing the lower intake gasket and after. It also accelerates on it's own when driving, like the cruise is on. Ive changed both the upper and lower intake gaskets, throttle body gasket, idle control sensor, throttle position sensor and cant find any vacuum leaks. The linkage to the throttle seems to be ok and when changing the gaskets the EGR valve didn't look blocked up. The temperature gauge is very erratic and moves up and down contantly. I'm wondering if the sensor for the gauge could cause the computer to think the engine needs more fuel. Anyone had this issue and found a fix? Any info would be greatly appreciated.

 

Welcome to the forum,
some movement in the temp gauge is normal, as for the idle you might want to clean and inspect the IAC and TPS and clean up the throttle body plate and return spring, just some places to start...

 

The IAC and TPS have both been replaced and the throttle body cleaned and reinstalled with new gasket when the upper and lower intake gaskets were replaced. As of today it no longer idles well at startup and then goes high once put in gear like it did yesterday. Ive started it several times today and it's high all the time now.

 

ECM is bad. Having several random electrical issues since last post