Engine/Transmission (1998.5 - 2002) TPS and throttle bucking

[GiesJ]

Posted in 911 but haven't heard much:



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

 

[GiesJ]

Could this be related to having 1. 6s and no boost fooler currently??

I ran without the Comp (as an EZ only) for the past few months without this problem until last week.

VP44 change went great and also changed LP. Got to be something electrical because of the dash temp gauge.

Please help!

 

[GiesJ]

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.

 

[GiesJ]

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