Archived TPS/bucking Surging

[GiesJ]

Received a P0123 before and after changing a dying VP44. Before and after VP truck would buck and surge violently after some time of driving. Approx 10 minutes and the throttle has a life of it's own. Continue to have problem after VP44 swap. Was able to swap the TPS/APPS with my buddy's truck and have the same problem with a good TPS/APPS. So I have ruled out the TPS for the moment.



Here is the funny thing, my temp gauge craps out at the same time my throttle gets possessed. IF the gauge is reading temp the throttle works fine. If the gauge is not reading, throttle is fubar'ed.





Questions --

Has anyone had a similiar problem and see it tied to the temp gauge?



Is there a schematic of all of the grounds on the truck somewhere? Seems like I should check all of those.

Any and all help is greatly appreicated.



1998. 5 24V 5 speed with 150K, BD brake, 1. 6 EDMs.

Jason

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[John - K5AWO]

It sounds to me like you have bad ground issues.
I would start with removing the battery terminals, cleaning them real good and smear some good battery post grease on them to prevent future corrosion. One such grease that I use is Novoxid. Hard to find. Then I would find all of the body ground straps on the truck body, and clean them up and smear them with the same grease.

I do this on an annual basis as a PM thing. The trucks pull a lot of current when the starter and grid heaters are in use. Bad grounds can cause all kinds of weird issues.

Just a thought. Can't hurt. Might help.

 

[GiesJ]

John -

I did the battery terminals thing just this week. Can you help me find all of the body ground straps??

Thanks for the reply. Sure hope to get her dialed in...

 

[TravisG]

I am not sure if I can be of much help with the temp gauge thing, but if the truck is an automatic it could be a governor pressure solenoid. Might be something to think about if it turns out not to be a ground issue.

 

[GiesJ]

Thanks for the idea. Truck is 5 speed though...

 

[GiesJ]

Moderators - I have this posted in 24V also. Please delete if it is in too many places.





OK, Problem has escalated and now when I turn the truck on it runs away (redline).



If I unplug APPS sensor, truck starts and holds idle fine.



Checked my grounds and I have 0 ohms with truck off on Pins 1 and 4 which are Battery voltage for the idle switch and APPS ground. Does this sound normal? Of course the APPS ground should be ground but what about pin 1?



When I turn the key on, but truck off, these see 46 and 45 ohms respectively. With key on and truck on they both see 85 ohms. Another dumb question but why the continuity change with truck on?



Also checked voltage on terminal #5 - APPS supply voltage and have a constant 5. 07 +/- . 01 volts. Key on truck off or truck on sees this same voltage.



Any insight greatly appreciated. My manual states to replace APPS at this point. Did that yesterday with a borrowed APPS (from a 99 24v Auto - note mine is 98. 5 manual) and still had the same problems. Do not think it is the APPS.



Oh yeah, coolant temp sender is now acting normal...

 

[GiesJ]

I've been searching and reading. No luck. Could this be an ECM problem??

 

[mgoncalves]

Boy, I would replace the APPS. Just because the APPS works okay on his truck does not mean it is okay for your truck.



If it were me, I would get a new APPS and then trouble shoot from there. With these trucks, the APPS is always at suspect anyways, so a new one is never a bad idea.

 

[Gary - K7GLD]

It's not too uncommon for there to be corrosion or poor contacts at the ECM plug - sure wouldn't hurt to unplug it, carefully apply a good blast of tuner tonic into both male/female ends and re-assemble...

 

[GiesJ]

Boy, I would replace the APPS. Just because the APPS works okay on his truck does not mean it is okay for your truck.



If it were me, I would get a new APPS and then trouble shoot from there. With these trucks, the APPS is always at suspect anyways, so a new one is never a bad idea.

Good point. I would think with his APPS on my truck I wouldn't see the same exact problem. At the time it seemed like a good way to not spend $500.

 

[GiesJ]

It's not too uncommon for there to be corrosion or poor contacts at the ECM plug - sure wouldn't hurt to unplug it, carefully apply a good blast of tuner tonic into both male/female ends and re-assemble...

Will try. What's "tuner tonic"?

 

[Gary - K7GLD]

Will try. What's "tuner tonic"?

It's a spray on/in contact cleaner that cleans, lubes and protects electronics contacts from corrosion and poor connections, was used extensively by radio/TV techs to clean volume controls and the rotary turret tuners in TV's - thus the name "Tuner tonic" - I always apply some whenever I take connections apart - it's available in spray cans from Radio Shack...

 

[RBeard]

APPS=$368 @ Hoesli Diesel,Just got one

 

[GiesJ]

RBeard - I swapped out my buddy's APPS and had the same dang thing happen...

Thanks for the lead on a good price should I need one again though.

Jason

 

[GiesJ]

After some more reading I chose to have it taken to the dealer today. They said the ECM (P0606) looks to be toast.

I think I am going to change this myself as they are quoting a hell of a lot of money for one...

Thanks for the input here. Hope this solves the problem.

Jason

 

[GiesJ]

New ECM and check engine is off and truck runs (fingers crossed) great!

Special thanks to Bob Wagner for overnighting one for me to try.