I have a "98 with a 5.9. It has a little bit of a rough idle. I replaced the plug wires, plugs and plenum gasket. I also rerouted the plug wires per the TSB and put on a 180 thermo. It seems worst when I come to a stop after running at cruise speed for a while. At low speed, it will eventually smooth out again.

I am fearing a crack in the head. I am thinking that maybe the crack widens when the engine gets hot then becomes less noticable as it cools. I don't know if they work that way.

I guess the best way to know would be to take the heads off and have them magnafluxed. Does anyone know af another way to check?

Does anyone have any other ideas about what might be causing the rough idle. It really doesn't idle that rough. Just feels like a slight miss. There are no engine codes.

 

i am having the same trouble only mine surges and attempts to stall out then it settles and goes back to idle----this all just happened since this past weeked check out my thread-----I have no luck so far sorting the trouble----if you find out what it is post up....

my thread: https://dodgeforum.com/m_428067/tm.htm

 

Ill let you know what I find. I am planning to decarbon the engine today. Shaould have done that after the plenum gasket. I also need to replave the airbox gasket. I forgot that it had a split in it when I was rushing to get averything back together after the plenum gasket.

 

Try cleaning the iac. It could be gummed up and sticking.

 

I agree, before doing anything to serious take your TB off and clean it really good.

 

Guys. Thanks for all the great advise!

Today, I replaced the brake pads, and sway bar links. Then I rep the airbox to TB gasket and cleaned the IAC. I had cleaned the TB pretty toroughly when I replace the plenum gasket.I also decarboned the engine with Sea Foam.

I still get a little bit of a rough idle but it really isnt too bad. Maybe the truck just runs a little rough. I guess Ill just wait and see if anything gets worse.