I have been having an iddling problem and I cant figure out what it is, here is what happens;

whenever the truck is in park iddling the rpms loop (go up than down, then back up and down ...........), the truck also seems very sluggish taking off and I cant hardly keep it at 70 MPH in the highway specially going up hill.

here is what I have done;

new plugs, distributor, rotor and wires
new IAC valve
new TPS
Cleaned the TB, and did a combustion chamber cleaning (with the mopar stuff they sell at the dealership)

here is what I have:
97 1500 dodge ram
automatic 4 spd
3.9 L

is a faulty PCM a good assumption?

 

No I don't think it is the PCM sounds like a vacuum leak. My guess intake manifold gasket. It is very popuar in the ram to have this issue. Check the rest of the lines but I think manifold gasket. With the truck running spray some throtle body cleaner on the vacuum lines and where the manifold meets the top of the head when the idle changes thats where the leak will be.

 

i have to agree withthat. i doubt its the PCM.

 

Sounds like you threw alot of money at this thing. And I concur...Vac Leak!

 

thanks, I will try that. it also it just came to me, all of this started happening after the tune up so I might have unhooked something. I will give that a shoot and let you all know how it goes.

 

Check your plug wire routing too, especially 4/8 and 5/7. They should not run parallel to each other and keep them far apart as possible. Still think its a vac leak though.
WC

 

well I have the 3.9 V6 and I tought for the routing on this one I only had to worry about the coil wire not being close to any of the other wires, is this correct?

 

Sorry, my bad. Thought we were talking about the 8.

 

no problem, I will make sure i check that to, when I replaced the wires, the coil wire i bought at the dealership was almost too short, so maybe I will get a longer coil wire and make sure is an 1" away from everything else.

 

Have you reset the PCM since this has happened? Unhook the battery for a few mins then reconnect it.