Engine/Transmission (1998.5 - 2002) Studdering, missing, hesitating

[bikinjoe]

Hi all, I seem to have a issue with my truck I can't get resolved. I've searched the forums over the past month and replaced and/adjusted some parts based on that info I could find.



The problem: Shortly after starting the truck, maybe 10-15 minutes, I get a hesitation or missing, it seems to be just shy of the 180 degree range. I also had what to me felt like a dead pedal.



I pulled some codes from it and it showed the MAP being faulted.



I replaced my Boost Sensor (MAP) and that seemed to get rid of the dead pedal. (I tried cleaning it first and no success). But the hesitation remains.



I went through the APPS trials, adjusting it to the right voltage (which I was only off by . 003) and also the drilling and spraying with contact cleaner. Still not better.



Last night I put it on Cruise when it started doing it and the hesitation remained and from what I read if the APPS was bad the problem would go away.



I stopped at the store and when I got back in the truck the problem was gone.



I have not had the ECM flashed yet, a local shop has no ideas, and I'm at a loss.



I don't mind buying the parts if they fix it, but I don't want to buy parts that are not bad.



Any thoughts?



Thanks, Richard

 

[0013]

Whats your FP? Maybe your transfer pump is intermittent (sp).

God bless,

chris

 

[rkressg]

Change your fuel filter.
Does you Lift Pump put off any pressure?
Could be your IAT (Intake Air Temp) sensor?

Are you certain that there are no codes?

 

[bikinjoe]

FP is running at 10-12psi, had that checked last week. Lift Pump seems to be okay. There was a code for the MAP but after that got replaced it was cleared and nothing new has shown up. I have a reader and have checked a few times.

I have changed the fuel filter, than the shop did it as well.

I did not replace the IAT sensor yet, I cleaned it and nothing changed. I think that is the next step.

I've seen some talk about the ECM? being bad, how common is that? also does it sound like the APPS could be okay sense I put it on Cruise and the problem remains?

Thanks so far for the help,

 

[bikinjoe]

I replaced the IAT sensor tonight, went for a test drive and no studdering, going for another drive in the morning and if all goes well hooking up to the 5er and headed up to the hills for a few days

thanks again for the suggestions.

 

[bikinjoe]

Well, still no luck. it seemed to be better after the IAT and then it wasn't. So I got a Pedal Position Sensor, $400!, thinking that was the next step and still the same.

Now it's more steady, cruise along at whatever rpm and it acts like it is starving for fuel. I step on the pedal and it goes like nothing is wrong but at the steady speed it is jerking and missing like crazy now.

Any other thoughts out there? still no codes, FP is still around 10psi according to the gauge.

Thank you.

 

[rkressg]

Maybe a bad injector???

How many miles are on your injectors? Does it have a lumpy idle?

I did not notice, but do you have an Edge Drag Comp? It is rare, but sometimes they will kill a VP44 for absolutely no reason.

 

[bikinjoe]

I was wondering about an injector, I'll search but is there any way to test them? No Edge, all that is stock so far. There is about 125k on the truck, and I don't think the Injectors have been changed.

Idle seems to be okay, a little gas and it starts the studdering.

Thanks for the idea.

 

[rkressg]

A good diesel shop should be able to pop test the injectors. I believe they should pop at 300 bar or pressure. For the cost, you could consider just upgrading the injectors to a new set of something more powerful.

Is your tachometer working? I am thinking a possible issue with the Cam sensor.

You could also have some type of issue with the VP44, maybe in its early stages of failure. Something is happening and maybe it is timing related. You don't have a P1689 code?

Are you checking both the PCM and ECM for codes? If you are using a scan tool, you might have to select to scan the different computers (depending on the model of scan tool). If you are just using they key cycle method, make certain that you wait for both the PDone and EDone.

 

[SGrasmick]

I am experiencing a similar problem with a bad studder in power and its intermittent, onoly with my TST on higher levels, TST claims the Box wouldnt do this, Just replaced the VP due to codes and failure.

Heres the tricky part, I used a scanner and got NO CODES Cycled the ignition the magic 3 times and got a few codes some transmission related due to my DTT voltage regulator Others included a p0122 and p0622 voltage and Apps related codes was told to try the MAP sensor if not ill try the APPS like you did.

Getting to the point, how are you checking codes on the truck??
My OBD II Scanner did not pick up these codes.

Hope that may help

 

[bikinjoe]

Thanks again for all the help, I tried the ignition trick, as well as the scanner with no luck on the codes. Broke down and took it into a shop on Monday, turns out it is the lift pump on producing around 1/2psi once it gets warm, started out around 4-6psi cold. They checked everything else out and the VP seems to good, as well as the injectors. So I see a new system in my future, FASS or something, got to do some research now, see what's what.

Thanks again, hopefully this solves the issue, my 5th wheel is getting lonely...