98 v6 engine races on it's own

[recian]

I've had idle issues with my 3.9 for awhile. It likes to race when I tap the gas just alittle. I've watched with the air filter off and the throttle plate is closed when this happens.

It's revved to almost 3500 on it's own before. It'll stay revved up until you tap the gas too. Kind of dangerous in drive moving through the neighborhood at times. It also has developed another weird problem. It will idle at around 800 when cold but 1300 when warm.. So it's reverse of what it should be doing. It likes to stumble and stall when shifting into drive when cold due to low RPMs.

Coolant gauge on dash works fine and I replaced IACV and TPS a few months back and re learned PCM with DRBIII

 

[emjohn4]

Air idle motor and / or vacuum leak.

 

[dodge dude94]

^Agreed. Regardless of whether or not you replaced the IAC and TPS, if you don't put the right brand on these trucks it'll still behave like crap.

 

[recian]

I've swapped a working iacv from another v6 so I'm leaning toward vacuum leak. I've heard the intake gasket is common. This one has 330k miles and looks like nobody has been into it.

 

[dodge dude94]

Well, if you swapped another known good IAC, then yeah, that rules it out.

Plenum leak is possible but is it burning any oil?

 

[recian]

Surprisingly no its not losing any oil. Doesn't even put out A blue puff at startup just seems to run a little rich by the smell and if you listen at the tailpipe it seems to rumble like the older Mopar big blocks. My Dad says it sounds like its got a burned valve.