I have a 2001 2500 with a 5.9L V-8 i have just replaced the tps and the iac valve.recently my truck idles rough and misfires at idle every once in awhile,and it also stalls when im idling up to a stop. and it also stalls sometimes when im trying to start it up. my question is would this be thw cap and rotor? Or the plugs and wires or both? they are about 30000 miles old. thanks

 

i have the same truck but mines heavy duty, not sure if yours is, anyway i was looking through the dodge manuel and it says to replace the spark plugs every 30000 miles because its heavy duty.

 

if it's 2001 it's heavy duty. They only made light duty 2500s in 94, 95 and maybe 96.

 

did you reset the pcm after doing tps and iac. if not try that first. disconnect neg battery and turn ignition to start for 30 sec.

if that doesn't help, i'd try plugs, wires, cap, and rotor next. cap is hard to get to. note position of the #1 marked on the cap. change wires one at a time, take your time and don't get them crossed up. double check #1 and firing order both before and after.

if that doesn't help, i'd try chevron techron fuel injection cleaner for a couple of tanks.

if that doesn't, id try pre-cat o2 sensor next.

if that doesn't help, i'd probably carry it to a shop and have them put in on the diagnostic computer and see whats wrong.

 

The Intake Plenum gasket is known to go bad on the Magnum motors causing roughidle, poor performance, poor MPG, and increased oil consumption. Basically the problem is,the intake plenum is steel and the intake is aluminum and they react differentlly to temperature changes. This causes stress on the plenum gasket and tears it and allows oil to leak into the plenum pan. It also causes vacuum leaks and leads to rough idles.

There is a TSB on this but I cannot find it right now, but there is tons of on-line info about this problem. The dealers did literally thousands of these under warranty, but the problem will happen again due to the poor design and the use of dissimilar metals.

Hughes Racing makes a thick aluminum plenum that replaces the stock steel pan and cures the problem. It requires removing the intake and flipping it over and replacing the plenum pan and gasket, so it's not for everyone to try this, but if you have a weekend to take your time and can follow directions, check out hughes. Or buy the Hughes pan and install kit and take it to your local engine mechanic. The plenum gasket labor flat rates at like 4.0hrs so be preppared to pay close to $500.00 + the kit to have someone else do it.

That is of course if thats what your problem is. Do some searching and you will find some info on ow to check it. You can shine a flashlight down your throttle body and look for signs of oil on the top side of your plenum pan, but it's hard to see the entire surface area. There is also a way to check it with a vacuum test, but I cannot remember how to do it.

 

thanks guys for all the answers, i checked for the plenum leak using the vaccum test, and i was wondering if the hose that connects to the intake on the passenger sideshould be sucking air or blowing air when i cover up the hole where the pcv valve is?

 

short answer. neither blowing nor sucking. it should be neutral.

long answer. when pvc is connected to intake manifold (drivers side on your 01), its sucking air through the engine, and pulling in fresh air on the passenger side, through the breather hose. so with pvc connected, you'll have a little, not much vacuum at the passenger side hose. with pvc disconnected (and sealed), there should be no vac. if you have vac, then the plenum is leaking, creating an out of control, unmetered, vac leak that sucks air and oil out of the lifter valley.

 

well it isnt alot of vaccum coming out of the hose on the passenger side, if i put my finger over that it builds upbut it is still very little. would that still mean the plenum is bad?

 

take off air hat and filter.. hold open the tb and look down inside with a flashlight.. see if theres oil pooling up.. even a little bit... if there is.. plenum is blown.. if its basicaly dry .. but dirty.. (kinda looks sticky) it should be ok