Hey all First time on here, trying to figure out a problem for my dad. He has a 1995 Chevy K3500 6.5L, and a problem has arose that even the previous owner (shop owner) cannot figure out. On startup the motor will idle at 2200 rpm and there is no throttle control, it is either on or off. It was checked by a snap-on diagnostic meter, Air filter checks, changed the TPS, all to no avail. Now I figured someone here may have had the problem and know of a way to fix it.

I appreciate any help and thanks in advance!

Any thoughts at all?

Most snap-on scanners don't work on a 6.5. Runaway throttle usually means broken armature in the injection pump. New, rebuilt or good used injection pump required. Send member Diesel Pro a personal message. He may be able to help with one.

^^could the APP throttle pedal be bad and causing erratic voltage signal to PCM (thinks the pedal is in different position than actual)?

unlikely....but is the idle tied in with the coolant temp(ECT). like the PCM thinks the truck is always cold?

^^could the APP throttle pedal be bad and causing erratic voltage signal to PCM (thinks the pedal is in different position than actual)?

unlikely....but is the idle tied in with the coolant temp(ECT). like the PCM thinks the truck is always cold?


Possible, because he said after a couple hours it will step back down to 600 rpm, but still no throttle control just wide open or off, I dont deal too much with diesels, but the what he described it, all the throttle control is done electronically, so it is possible the PCM may be whacked a little bit....

You can try a known good APP pedal(from a friends truck or so?)
I that dont solve it ,could be IP ,but cant rule out the ECM either.
Cold idle is ECM controlled based on CTS signal,but cold idle is only 8-900 rpm or so.

Busted teeth on a RPM sensor or failure with it / wiring?

PMD shorting out and allowing the throttle to be open? Wiring doing same?

What parts were changed other than the TPS?

Hey all First time on here, trying to figure out a problem for my dad. He has a 1995 Chevy K3500 6.5L, and a problem has arose that even the previous owner (shop owner) cannot figure out. On startup the motor will idle at 2200 rpm and there is no throttle control, it is either on or off. It was checked by a snap-on diagnostic meter, Air filter checks, changed the TPS, all to no avail. Now I figured someone here may have had the problem and know of a way to fix it.

I appreciate any help and thanks in advance!

let me take another go at it...
so the truck is inoperable?
no ses codes?
does the truck have fresh fuel in it?
you chnaged the TPS?...there is no tps I believe on the 94-up trucks.
only the mechanical 6.5s had a tps sensor.hmm...so which part was changed?

let me take another go at it...
so the truck is inoperable?
no ses codes?
does the truck have fresh fuel in it?
you chnaged the TPS?...there is no tps I believe on the 94-up trucks.
only the mechanical 6.5s had a tps sensor.hmm...so which part was changed?


I'm trying to get him to get on here and respond so we will see if he does...but this i know...

The truck starts up and just sits at around 2000 rpm, pretty much inoperable.

I would assume they pulled no codes, as the previous owner actually owns a towing service and a shop and pulled no codes.

The truck has been being used as a daily driver so yes there was fresh fuel.

Not sure about the TPS, but he said he replaces it, but I guess if it is electronic it may not have a "position sensor".

Other info, It is not the kick up switch stuck or anything, that would only go up to 1000 rpm anyways...

I'm seeing if I can get him to sign up on here and answer some questions, hopefully he will, my knowledge is limited with the situation.