Throttle-by-wire problem, 1996 6.5

[winemaker]

Howdy all: My throttle-by-wire is worn and is very difficult to drive smoothly. It seems like the throttle is either on or off. I read a link where the writer removed his, drilled a hole in the plastic case, sprayed in some electrical contact cleaner, resealed the hole and reinstalled with success. I love these money-saving tips on this site and I've payed for my membership many times over with tips like this one. Before I proceed, however, I wonder how many others have had success with this method or other methods, and is there a risk of hooping it completely rendering my truck undrivable until I replace it?
Is this failure inevitable? ie should I try a wrecker for a used part, or is that merely a short-term solution? How many miles are people typically getting before this part wears to the point of failure? Thanks for any input! Cheers! Brett

[DmaxMaverick]

Is your "Service Throttle Soon" or "Service Engine Soon" IP lamp on?

If not, the problem with your pedal is mechanical, not electrical. A good cleaning should take care of it. The pedal has a built in fail-safe. It has 3 pot's in it. If one fails, it will illuminate the lamp, and drive normally. If 2 fail, it will "limp". If all three fail, it will shut down. There's no reason to believe one failure will lead to another, unless a mechanical misallignment or dirt is wearing them out. If you don't see the lamp, scan for DTC's to confirm the code is not present, and you don't have a malfunctioning lamp.

If the lamp is on, how does it drive?
Try cleaning it. If the lamp goes out, you fixed it. Even if temporarily. A terminal failure won't be corrected, and you'll have to replace it to get the light to go out.

[Robyn]

Blessed be thy DB2 Mechanical pump and a new cable hooked to a fresh shiny new pedal assembly.
I have had TPS's go south and it sux. Ruined a trip for us and had to wait a few days to get the new unit. Limped home real slow for 80 miles but it beat walking or a hefty tow bill.

[winemaker]

Thanks for the insight. No SES or service throttle lamps on. I guess I'll check for a code. Happen to know what code it might be? As far as cleaning the assembly goes, would I take everything down to the paint or bare metal, then smear some never-seize on it and reinstall?
It drives very nicely otherwise, but it seems that I can't hold a steady pedal unless I'm lugging it slighly or already doing highway speeds. But to try to drive 35 MPH in third gear is almost impossible. I have to apply just the lightest touch with the right foot and this causes acceleration, and as soon as I let off, it's like watching someone who has never driven a stick bunny-hopping down the road. So into 4th I go. Anything above say 1800RPM is ultra-touchy up to about 2500 or better. Thanks again. Cheers! Brett

[winemaker]

Thanks for the insight. No SES or service throttle lamps on. I guess I'll check for a code. Happen to know what code it might be? As far as cleaning the assembly goes, would I take everything down to the paint or bare metal, then smear some never-seize on it and reinstall?
It is almost impossible to maintain 35MPH in 3rd gear. The slightest input on the throttle pedal causes it to speed up, and as soon as I let off even slightly, she starts bunny hopping like a guy who's never driven a stick. So into 4th gear I go and run at like 1400 RPM to smoothly maintain around-town speeds. Seems like the ultra-touchy range is anything above say 1800 RPM up to 2500 or better.
Thanks again. Cheers! Brett

[winemaker]

Sorry for the repeat...I thought the first one didn't post. He he. Brett

[garre1tt]

Lost my mid range about a year ago. did not try the cleaning but did find a new TPS on ebay for $125 and has worked great.
the truck never set hard code but did store one for the throtle.
Michael D.

[winemaker]

tps = throttle position sensor?

[DmaxMaverick]

tps = throttle position sensor?

Yes. But not what you have. The TPS is for mechanical injection pumps, with the sensor on the pump linkage (which doesn't exist on DS4 pumps). You have an APP module, the pedal module.

[winemaker]

Thanks again DMax.

[Kennedy]

Very seldom do these actually go bad. If the engine runs past the red line in Neutral, this is a dead giveaway that the pump delivery control is sticking...

[winemaker]

I tried to rev it past redline in neutral today, twice for good measure, and it wouldn't over-rev. Does this eliminate the pump delivery module, or is this just one method of diagnosis, therefore said module may still be failing?
Also, what does APP stand for and where is it located? Thanks again for you inisght. Brett

[DmaxMaverick]

APP = Accelerator Pedal Position (Potentiometer) module. It's your go pedal.

[Kennedy]

I tried to rev it past redline in neutral today, twice for good measure, and it wouldn't over-rev. Does this eliminate the pump delivery module, or is this just one method of diagnosis, therefore said module may still be failing?
Also, what does APP stand for and where is it located? Thanks again for you inisght. Brett


Not so much TRYING to go past redline, just try to bring it up slowly and see if it takes off on you.

[winemaker]

Yes, that's exactly what it does! If I try to hold certain revs, say 2000 RPM, the revs keep increasing without the added input from the right foot. I apply just enough pressure on the thottle pedal to increase the revs, but it reacts like I'm matting it. To be clear, it idles fine. It only runs away when I've got my foot on the pedal. This to you says Pump Delivery Control, eh? (the Canadian in me)
Can you tell me where it is and what I need to do to re & re, as well as give me your oppinion as to any aftermarket vs stock units, if any are available, or used units from the wrecker, please? Also, what sort of ball-park price should I expect?
I scared the crap out of some guy in the Safeway parking lot this morning! As I was rolling slowly past the front of the store in 2nd, it started increase revs on me, so I let off the throttle causing the tires to chirp upon immediate slow-down, and this guy thought I was going to run him down. Not only did I feel a little sheepish, this kind of stress can't be good for things like u-joints and motor/tranny mounts, etc....
Thanks again for your time and know-how. I'm a small-business man working 6 days a week and my son is about to enter daycare, so time and money are at a real premium at this point in my life. I really appreciate the help! Cheers! Brett

[gwaidman]

Howdy Brett. As you and I have discussed, it may be the optical sensor in the IP. I believe there is a way to 'hotwire' around this as (correct me if I'm wrong here). Who here has done this and what was the proceedure? Success stories and failures welcome.