I Recently Purchased An 04.5 3500 Auto...after A Few Weeks It Has Begun To Surge/stumble At Light Steady Throttle Mostly 30-50 Mph..at Times The Throttle Seems Momentarily Dead And Then Accelerates Again....the Really Stupid Thing Is This All Started After I Degreased The Engine And Got Everything Good And Wet...but The Problem Persists Days Later..i Changed Fuel Filter But Still Same..it Had The Lift Pump Mod To-tank About A Year Ago I Am Told..should I Suspect It??

 

My 04.5 2500 does the same thing to me it's been in the shop and they said nothing was wrong with it.Another member suggested getting a fuel pressure gauge to monitor any fluctuation possibly the lift pump?Also my wait to start light does not wait anymore are you having the same problem there?

 

the wait to start light does wait if the engine is cool enough but lately been 70-75 degrees even at night so you never see it wait at all... new info tho on the surge.. a good local shop tested lift pump preasure and all is good..it seems the tps sensor is not communicating correctly with the ecm and needs reflash..will know tomorrow if its all b-s or not...

 

Let me know I've had people suggest the Crank Shaft,Camshaft sensors, ECM,lift pump,and finally injectors?Not really sure which direction to go first?

 

Mine does this as well. I'm glad to hear I'm not alone. I am having the Cummins tech do some work on my truck this morning. I will be sure and ask him what he thinks it might be. I don't really see it as a problem, it just sort of feels like an old gasser engine that isn't warmed up. I can keep it from doing this by giving slightly more throttle.

 

Mines the same way if I give it more throttle it will clear up.It feels like it wants to die and then it will surge.Kinda like an engine thats not warmed up I agree.Let us know what he finds all the shops I've been to here must have monkeys working in the back because no one can figure it out.

 

Have you checked any of the connectors under the hood to see I there still might be some moisture in them since you said this started after you steam cleaned it. Just a thought...

 

Well, the Cummins tech did a bunch of stuff this morning and I asked him about this. I'm not sure if we solved the problem, but I think we improved it some.

Me and the tech and the transmission tech got to talking about this issue and they were saying that it sounded like it might be transmission related. We took the trans pan off and they checked for play in the band. Sure enough, they said my band was extremely loose and that I was lucky I still had second gear (which is mainly where I feel this surge). They tightened up the band as much as they could, and just on the ride home IMO the problem still exist, but it seems less intense... So in this aspect, I would conclude that there is a relation between the tranny and this surge, although I would say that this is NOT a cure.

To make a long story short, it's amazing what a difference there is in the general knowledge these two well qualified techs had as opposed to what I thought I knew from reading through forums for the last 3 years. I really thought I knew my stuff just from reading. Not so. These guys that actually have worked on these engines and transmissions day in and day out for years know WAAAAAAY more than me and most all of the vendors I have seen on DTR and TRD.

After listening to the transmission guy for a few minutes, I decided then and there that he would be the one to upgrade my transmission in the next month or so and the Cummins tech will be doing my other mods. I learned things about my truck that I have never even heard mentioned on these forums.

 

finally got so bad it threw a code..**** near quit and now almost undrivable over idle p2122 and 2121 throttle pos. sensor

 

What became of your problems?

 

So the throtle position sensor was the problem then.