Engine/Transmission (1998.5 - 2002) Trying to diagnose an engine miss / stumble...

[justinp20012500]

WOW... Common Problem



I have the same thing. It is just under mid acceleration. (About 20 psi in od, or drive locked up)



I have replaced the map, VP, and IAT. No change. When I unplug the EZ it goes away. I am going to try to swap EZ's and see if its still there with a new one.







Justin

 

[TORQUE THIS]

Just an update...



Last night we tried a different PCM, very little difference.



Also threw in a new VP-44 just for HA-HA's, made the stumble / miss MUCH worse.



Had the alternator tested, it's fine.



Could it be something mechanical now? Geez, I'm at my wits end with this thing!



Also drove around with a Snap-On scanner and it showed nothing...

 

[massdiesel]

Swap the alternator with a buddies, just because it tested ok doesnt mean its good have seen it before

 

[2-ND TIME]

mine also

I have a 99 do_g_ and it is the worst it bucks from idle up to 1600+ and has little power. Some thoughts on some of what was said that I can remember. Rear wheel speed sensor mine was replaced and it ran for about (8 hours) the way that a diesel should run. Don't think that it is the RWSS because it idles so bad . So don't think that there is an input from it at 8000 pulses per mile so that should be every 8 inches per pulse. Is anyone having a distance difference in the overhead display to the odometer with the original RWSS the two were out by about 275 meters (300 yds) (1350 pulses) and the new one is about 150 meters (164 yds) difference. So this is a buffering of 738 pulses. I do believe that this can be read on the DRB.

 

[ToolManTimTaylor]

Scott, Could it be a converter issue? I finaly got to hear it and it sounds kinda like a shudder. Could a converter lock / unlock that fast??? Say what the heck makes a 'verter lockup at speed anyhow (And no I do not want to hear lockup solonoid either!) I mean is it a check ball and spring thing that sends fluid somewhere thru a circuit type thang??



Behind the VP44 the cog that drives it, is that the gear that the cam position sensor reads? If so how? It's a magnettic sensor that has what a series of holes that pass it by that are machined into that gear or is it a tone ring setup? The reason I ask is what if a tooth or three are missing and the VP44 squirts fuel at the wrong times at upper rpm's because of a few missing teeth??



Or could it be cracked head between valves?? But then it would happen under higher cycender pressures and it happens light pedal , full load , even with the license plate upside down. I dunno just throwin stuff here OUTSIDE the sensor and electrical box here.

 

[jhyatt]

tim slow down

 

[ToolManTimTaylor]

Geez Joe I wrote that in a style you should easily recognize. 100 miles a minute . . all directions ... all the time Oo. :-laf

 

[Marco]

Did the test.

Too much time on my hands today...



I've done the voltage to VP test on my truck today.



In my truck the voltage stays arround 12. 17 Volt @ idle or moderate load, dercreases to 12. 00Volt @ WOT. BUT, one thing that's worth to mention is the fact that the Batteries are at 14. 15 Volt ... That means that the circuit that powers the VP has a voltage drop of about 2 Volt! WOW...



Marco

 

[TORQUE THIS]

Dan, it's been a year since I adjusted them, so I don't remember. It is on the list of things to keep ruling out. If I remember right, they were set between the acceptable specs according to the shop manual.



Marco, I haven't done that test yet, going to try doing it on Tues or Wed. I also have my hands on another alternator to try.



There are a few things that Scott (Massdiesel) has added to the list of things to rule out also. Scott, I'll call ya Monday afternoon.



LOL at ToolMan... :-laf

 

[Bob Wagner]

Mark, I know a guy in lower moose jaw that can perform an exorcism if it comes down to it :-laf



or maybe even a circumcism if needed

 

[TORQUE THIS]

Mark, I know a guy in lower moose jaw that can perform an exorcism if it comes down to it :-laf



or maybe even a circumcism if needed

OUCH! :{



I'm sure it's something REALLY stupid, usually is for me!

 

[Bob Wagner]

It was talked about yesterday, have you checked inside the tank for any problems?

 

[TORQUE THIS]

Funny you mention that, my little Choco Milk episode was brought up Friday night. I guess it could be worth a look if other things don't pan out.



For those that missed my blonde moment... https://www.turbodieselregister.com/forums/showthread.php?t=93326

 

[Gary - K7GLD]

I know you said you "checked injectors and tubes", but HOW did you check them? Could one of the injectors be hanging up or not have the same pop-off pressure as the others?



It's a lot of trouble, but swapping in another set would sure be interesting!

 

[TORQUE THIS]

Yup, been there done that, thanks for the input...



Stockers, mild and wild EDM injectors, stock tubes and modified ones.

 

[Gary - K7GLD]

Well, then I second Bob's exorcism/circumcision idea! :-laf :-laf

 

[TORQUE THIS]

The thing that really puzzles me is that it happens when adding fuel (via the TST), or with the TST off. (did the same with a drag comp)



The other side of the coin is that with a little moisture in the air or raining, it is at its worst. (TST off).

 

[Gary - K7GLD]

"The other side of the coin is that with a little moisture in the air or raining, it is at its worst. (TST off). "



That sure sounds like a grounding issue - especially since you have eliminated all the fuel related items.



On my truck, because of the Comp as well as my Ham Radio stuff, I have added ground straps from both batteries to the sheetmetal of the truck, as well as from the engine block to the frame and body - the factory uses anodized/coated bolts at a lot of their attachment points, and the anodizing process makes the bolts non-conductive...



That, and a poor connector somewhere in the wiring harness is about it...

 

[TORQUE THIS]

Gotcha again Gary, ALL the grounds have been cleaned, reinstalled and protected. I can totally disconnect the TST from all of its connections, and leave it miles behind on the work bench, still stumbles...



Just put new batteries in a week ago...

 

[HoleshotHolset]

That sure sounds like a grounding issue - especially since you have eliminated all the fuel related items.

Not so fast... I don't remember reading how Mark/Timmmarrrrrgh jacked up the bed and checked out the fuel tank sending unit.



Mark man: Have you tried sticking the inlet of the lift pump (the line/hose... not the pump itself) into a 5 gallon jug-o-diesel? That'll eliminate the sending unit and all of it's plumbing. Have you tried running the truck with a different lift pump... or - worst of all - NO lift pump? Running it for a bit with no lift pump won't hurt it terribly much. At least I won't see the damage from here... :-laf



Does milk curdle when it comes in contact with diesel fuel? Someone in WI must know the answer to that...



MTY