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

[kdunham]

I just cleaned every connector and ground I could see in the engine bay tonight,the truck runs alot better. That sure helps but from what I've been reading there is a very mysterious and common problem with these things not wanting to run right alot of the time. I don't think mine is 100% yet but then again I haven't put a VP44 on it or an APPS. Sauk Prairie huh? I'm in New Glarus,I used to live on the corner of 60 and 78 in Prairie du Sac,right next to the bridge on the river.

 

[HoleshotHolset]

New Glarus = hometown of my favorite local brew - New Glarus Brewing Company's "Spotted Cow". MMMmmm... cloudy beer.



It's a small world afterall... perhaps I'll see you around.



Matt

 

[TORQUE THIS]

Matt, I've got the PE4200, why run the truck without it hooked up?

 

[Gary - K7GLD]

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



DANG IT, you beat me to it!



Was laying awake last night, and got to thinking about the possibility of air getting sucked into the system somewhere between the tank and fuel pump - or even cavitation of the pump for that matter. I too thought about running a separate fuel line from an outboard fuel source directly to the fuel pump to eliminate everything downstream...



Sure will be interesting to see what the final outcome is from all this...

 

[ToolManTimTaylor]

Still feeling mechanical / converter related. The more I think about it I am ruling out cracked head between ports / vlaves. Hey Mark How sooty does your oil get?

 

[TORQUE THIS]

Hey Mark How sooty does your oil get?

Looks OK, smells normal...

 

[HoleshotHolset]

Still feeling mechanical / converter related.

Yeah... ? Then yank all of the plugs going to the transmission and rev it up in neutral... The converter needs electronics to cause fluid to go to the right places to enable lockup...



The lift pump could be the problem... OR, one of your AN lines could be sucking air. I'm still headed down the 'sucking air' route...



I'd be awefully tempted to run a line right to the inlet of the VP-44... with the loose end of that line dangling in a 5 gallon can of diesel chow... Just don't run it long like that and don't let it suck air...



Matt

 

[TORQUE THIS]

Well, I have -8 running the fuel system. ToolMan, all the -6 lines you had are at the shop, maybe it would be worth swapping all the lines out?

 

[ToolManTimTaylor]

Sure why not? Make sure they are cleaned out really good. They were and have been arround dust and cruddy grime for a while both under the truck and sawdust.

 

[Gary - K7GLD]

Just for a short test, some clear fuel hose directly to the VP-44 to monitor for visible bubbles would be a plus...

 

[TORQUE THIS]

Just another quick update...



Today being COLD! and dry, the truck ran GREAT! So... I'm really thinking its an electrical issue.



My next test is changing the sensor on the OD unit, and the rear axle...

 

[JoshPeters]

OK guys... ... Just an off the wall one that MANY guys miss. Check the alternator for AC voltage output. NOT the normal DC. I had a car at work come in..... 6th time in for an odd running complaint. The way this was explained to me is this... ... ECU + AC voltage = Drunk ECU. For every . 5volt AC the sysem just had a beer. Keep in mind the ECU is a lightweight. The car I was dealing with had 2V AC and Ran kind of like my Grandma. Good up to a certian point... then it would fall on its face and not get back up. :rollseyes: If you have access to an O-scope hook it up to the signal wire and see what the injection pulses look like. (I'm a 12v guy I don't know the 24's very well. Is that inturnal to the VP?)



I like Matt's air idea, but one problem, It should be more than one cylinder and the moist outside air wouldn't make a difference.



Josh

 

[Weidner]

any news?

I have a stumble issue on mine and inquiring minds want to know.

 

[TORQUE THIS]

Still haven't come up with anything yet...



Last thing to try is the alternator, this week I'm going to try a leakdown test.

 

[JaMan]

Keeping an eye also, got a local member that has the stumble at 1800 or so rpms at full lock in OD, with a 99 with a DTT 48re his symptoms started 1200 miles after the transmission install...



Jared

 

[Weidner]

Stumble Gone???

It might be, when I get a new truck. Test drove an 05 last night. I like my 2nd gen a lot, but the new shiny ones are sure nice. My lease is up in June, its either pay $18. 5 for this one or move on to an 05. It would be alot eaisier decision to make if I did not have this stumble... . and leaking oil pan, and worn out ball joints,track bar, tie rods ect.



Ohh the decisions

 

[Turbodiesel22]

My experience with the differential speed sensor when it failed on a 99 was a ABS and red brake light on constantly and no speedometer below 20mph. After 20 mph I had a speedometer which I assume is the speed sensor in the trans. Apparantly the trans, sensor picks up at 20mph and the differential anything less than 20. The differential sensor is about $45. 00. Don't know if this helps but if it would be a speed sensor I would look at the one in the trans. or the electrical connection to it.



Dave

I am not sure that I am doing this correctly, but I have a 99 with the red brake light and ABS light on and no speedo until the torque converter locks up at about 25mph, do you think this cud be the differential sensor on the fritz??????



TFields

 

[JHerrlich]

I'm going to keep an eye on this thread too. I have a stumble/bucking at moderate throttle also. Mine could be a whole different issue, though. My truck only does it when I'm slowly backing off, or slowing my acceleration. Either way, it's coming off throttle when it happens.



Mine could be related to the turbo, but I don't know.

 

[DavidC]

I am not sure that I am doing this correctly, but I have a 99 with the red brake light and ABS light on and no speedo until the torque converter locks up at about 25mph, do you think this cud be the differential sensor on the fritz??????



TFields

Unplug the sensor at the differential and put a ohmmeter across the sensor terminals. Should be somewhere around 1800 ohms. If it is bad usually a reading of open occurs.



Dave

 

[Weidner]

I guess threatening my truck worked. I drove all weekend with no stumble. My stumble was at heavy throttle 5th or 6th gear, like getting on the highway. It is deffinatly not doing it now. The only change, besides me looking at new trucks, is the weather. It is in the 60's now and no stumble. I think it has to be air temp related in my case.



The one question on the valve adjust got my attention too, I need to do that. I have not adjusted em ever. I guess now that the weather is nice, its a good time to get er done.