My truck is having trouble idling once the engine is warm. Especially when it's still in first gear and I let off the gas, the idle will drop so low that the truck will turn off. I replaced the IAC valve a year ago I think, but it was one from the local parts store and not OEM. Also, I replaced the thermostat recently with a 180 degree when I overhauled my cooling system. My temp gauge doesn't get too far about 130 unless it's idling in traffic for a long time. Could that be gumming things up? Or do I need to get a new OEM IAC valve?

EDIT: Also the engine is a 5.2 and was rebuilt a couple of years ago. Plenum was fixed then. Also, I don't run a catalytic converter.

 

I'd put a 195 back in. And you can try cleaning the IAC. https://dodgeforum.com/forum/dodge-r...n-the-iac.html

 

I have seen several cars & trucks act like yours simulating an overheating problem when they were not overheating. It turned out to be the EGR valve. If yours is electronic, it can be tested. If it is vacuum controlled, you can remove it & see if the rod in the base of it goes in & out freely, if not there is a carbon build up in the housing that can sometimes be cleaned out or just replace it. Check codes, fuses & all major electrical connections too to rule out the obvious small stuff first.

 

So if the IAC valve is bad, does the idle go up and down in park and neutral?

Mine is specifically dropping RPM's and sometimes dying when just cranking the truck up or letting off the gas in drive.

 

Yes, it can. Pull it and clean or replace. Follow instructions in service manual, and do not push, pull, or twist pintle - or you will have to replace it. It is a small stepping motor. Clean out IAC port in TB as well (will require TB removal).

 

my experience has been that failure to idle/stalling is usually the IAC and you can usually keep it running if you drive with both feet and keep pressure on the gas pedal. on the other hand - surging idle (1000-1500 rpm up and down, up and down), is usually TPS.