Engine/Transmission (1994 - 1998) Worn spot in my apps???

[mwilson]

My '97 is starting to have little fits when trying to get up to cruising altitude...



At 50-55 it is confused and shifts into OD, then out of OD, Converter Locks, then unlocks.



If I decrease or increase the throttle it will cut it out.



I can be going uphill, it will shift down, I increase the throttle and it will upshift and stay there all the way up the hill.



I say that there is worn spot in the apps.



What say you all???????



Mike.

 

[HBarlow]

Mike,

I experienced many APPS failures in my '01. The symptoms with the VP-44 APPS was always the same - no symptoms then sudden non-response to the accelerator pedal. By non-response I mean I had normal full range throttle control then suddenly none at any throttle setting.

I have not had any experience with it but have read many discussions on TDR of Gen II 12 valves of your model year with failing alternator or wiring connections. Corrosion can cause bad grounds or other erratic electrical issues. Yours sounds more electrical and automatic transmission related than APPS.

 

[mwilson]

I am not liking the TPS pricing that I am finding.



Being the experimental type I have ordered a Williams Controls TPS to try. I spoke with Williams engineering and the voltage, pins, and I think even the plug will match up.

It is cheaper.



I should have it in my hands Friday and will try to get it installed over the weekend, will let you guys know if it works.

Then I might be brave enough to post a part number.



Mike.

 

[HBarlow]

I hope you didn't spend more than $25. I don't believe that will be the cure - but I'm not a Cummins tech.

 

[mwilson]

I will test it with a voltmeter before changing it, I just wanted something ready to install if needed.



It is happening at the the exact same throttle position everytime, and that's why I'm leaning towards a bad spot in it rather than wiring/electrical noise or transmission internals so far.



Once you get it all locked and upshifted it is good for the duration of the trip. It doesn't hunt after that point.



If I get a clean and rock steady sweep of voltage when I test it then I will plan on dropping the pan and changing a few internal goodies... ...



Oh boy... .



Mike.

 

[cerberusiam]

Mike, you don't have an APPS. That is a 98. 5 and newer critter. You have a plain old TPS that is a pain in the back of the front.



There are several fixes that can make it serviceable but not neccessarily perfect. You can take it apart and clean it. Normally it gets crud built up in the spot it sets at all the time and won't make contact.



You can bypass it with a 10 turn POT on the dash to set and engagement voltage. Won't downshift until you drop below the preset but it cures the hunt problem.



You can do as you are looking to do, find another source for a TPS that will function as close as possible. That should preserve the functionality IF you can find one that runs the same distance and voltages as the PCM wants to see. That ends up being the tricky part is getting that narrowed and tuned in.

 

[cerberusiam]

I experienced many APPS failures in my '01. The symptoms with the VP-44 APPS was always the same - no symptoms then sudden non-response to the accelerator pedal. By non-response I mean I had normal full range throttle control then suddenly none at any throttle setting.

Thats because an APPS actual controls the fueling. A TPS does not, only senses throttle position to pass on to the PCM. All fueling is done with mechanical linkage.

I hope you didn't spend more than $25. I don't believe that will be the cure - but I'm not a Cummins tech.

Most of us would spend $100 for a sure cure. The $200-$300 for the factory part is the painful part. The only consolation, a TPS is cheaper than an APPS that essentially performs the same function. Not much of a consolation but some. :-laf

 

[mwilson]

Busted!!!

Yeah, I felt pretty stupid when I saw that I had titled the thread with APPS rather than TPS, but there was no going back once I hit the post button.



Hoping no one would catch it but you got me... ... .....



I was hoping that you would see it as this symptom also seems to show up with bad solenoids and transducers, but where it seems to be exactly the same throttle position time after time I am trying the easy stuff first.



I suppose it could be pulling the kickdown to a certain position as well, right??



Mike.

 

[HBarlow]

Thats because an APPS actual controls the fueling. A TPS does not, only senses throttle position to pass on to the PCM. All fueling is done with mechanical linkage.



Most of us would spend $100 for a sure cure. The $200-$300 for the factory part is the painful part. The only consolation, a TPS is cheaper than an APPS that essentially performs the same function. Not much of a consolation but some. :-laf

Thanks for the lesson. Again, I learned something about 12 valves.

I'm sure you know, an aftermarket supplier now makes the APPS and Geno's sells it. It is priced at about $150 instead of the $435 or similar I used to pay dealers for an APPS. Doesn't the same guy make one similar for 12 valves with a TPS?

 

[mwilson]

Most of us would spend $100 for a sure cure. The $200-$300 for the factory part is the painful part. The only consolation, a TPS is cheaper than an APPS that essentially performs the same function. Not much of a consolation but some. :-laf

That's the price range I am shooting for with this experiment.



Mike.

 

[cerberusiam]

I suppose it could be pulling the kickdown to a certain position as well, right??

Nope, OD and lockup is purely under PCM control. TV pressure only effects 1-2 and 2-3 shifts, nothing to do with lockup or OD.



Until the PCM grounds the circuit to fire the solenoids nothing happens. If by chance the power wire for the solenoids shorts to ground or tries to activate without prior approval, trans goes into limp mode or you let the smoke out of the PCM. Either way different set of symptoms.



The PCM\ECM\SBEC or WHAT ever it is called in a 12V, they had several :-laf, looks at voltage from the TPS and the voltage from the speed sensor and decides based on the tables when it should call for OD. The stupid VSS, which is just a Hall effect sensor, will cause the exact same symptoms so it is a pain at times to figure out which one really is the issue. On a 97 that is the switch over from VSS to ABS sensor for speed. Not sure if it was all of 97 or only part of the MY.



The speedo will never show an issue but the signal is not good enought for the computer to hold OD and a huntin' we go.

I'm sure you know, an aftermarket supplier now makes the APPS and Geno's sells it. It is priced at about $150 instead of the $435 or similar I used to pay dealers for an APPS. Doesn't the same guy make one similar for 12 valves with a TPS?

Yep, the Timbo APPS is all we buy for the autos. He still does not make one for the manual CR's though which means a dealer trip or lucky enough to have one matches the Timbo. I think the 24V's used the same one but the CR's moved the APPS under the battery for the manuals and usually used a different style.



The real crime is the price that is charged for a simply potentiometer cuz that is ALL a TPS or APPS is.

 

[mwilson]

Well, it's here.

I don't know for sure if it is clocked right or not, but looks like it might work.



Here are a few pictures... .





Mike.

 

[mwilson]

Back to the drawing board......

Ok, took the TPS off last night. It was dirty!!!



Compared the old one to the Williams and everything is a match other than the ROTATION!!!!#@$%!



So back to the books today for another try.



But we drilled a hole in the old one and cleaned it up, now it shifts perfectly so my diagnosis was right in this case.



Will let you know when I find an affordable replacement.



Mike.

 

[HBarlow]

Mike,

Congratulations on expert diagnosis. My apologies for initially doubting your direction. I wrongly assumed the TPS works like the APPS in 24 valve engines.