Engine/Transmission (1998.5 - 2002) Rough idle and high idle and rough when warmed up

[Sticks]

What????
A vacuum leak from the vacuum system has no effect on engine speed. There has never been a vacuum input to the apps. You have me lost lol

Bob, I did not say a leak in the system, I said a leak in the VALVE that controls the cruise- READ - the valve is not closing all the way and a slight vacuum is being applied to the mechanism that pulls on the throttle linkage inside the APPS housing ergo increasing the RPMs.

Which is all academic anyways, the problem went away with the borrowed ECM, thus the likely culprit.

 

[Bob4x4]

Bob, I did not say a leak in the system, I said a leak in the VALVE that controls the cruise- READ - the valve is not closing all the way and a slight vacuum is being applied to the mechanism that pulls on the throttle linkage inside the APPS housing ergo increasing the RPMs.

Which is all academic anyways, the problem went away with the borrowed ECM, thus the likely culprit.

That does not happen-but nice try

 

[21skippy13]

Okay so I finally got the new computer, got it in today and the high idle went way, drove the truck about 20 mile and so far no high idle.
BUT still has its rough idle, it's not noticeable while your moving faster than 10mph or so but anything less obviously keeps the truck at a very low rpm and you can notice the engine roughness, or if you cruising and take your foot off the throttle you can also notice the roughness but barely, until you come back to a stop or idle and it is rough, shakes the truck too lol

 

[VolsFan]

If still having rough idle, almost has to be fuel delivery. My 99 had that exact same (shaking/backfiring at idle) issue with a reman. injection pump with a one yr warranty on it almost expired. I didnt void the warranty by tapping the pump wire and never let it get less than 10 psi of fuel. The shop examined it and agreed, got it replaced for free, including labor. I ran that thing running rough for a few months though, decided to get it checked out before the warranty ran out. Its possible there may have been damage done to your VP with pressure getting down to 3 psi, sometimes it takes a while for them to die, others leave you stranded on the side of the road.

 

[Sticks]

Now, your fuel pressure is way to low, and I am surprised your VP is not toast yet. 3psi is not "kinda OK", that's bad, and sound about right for the in-tank pump. Dodge says it's OK, but it's not. 10psi minimum at WOT. Get that fixed first. Either after market transfer pump (FASS, Raptor... ), or the combination of the in tank dealer update in combination with the block mounted OEM transfer pump.

Next item to address!