Hey guys so this pretty much all happened about a year ago, I was cruising home ( nothing crazy) when all of the sudden the truck started surging and gaining MPH/RPM. Limped it home it would just randomly spike RPM to redline sporadically and come down to idle. changed fuel filter and seperator (FASS) and found my FASS had a popped fuse, fixed that. 16 PSI of fuel pressure, no CEL and issue still occured. Put a scan tool on it and the scope showed spike in voltage on ECM, APPS, and VP while the RPM jump was happening. Im leaning towards replacing the ECM. The truck has been off the road for nearly a year now from this and really want to get it back running. Has anyone run into an issue like this???

You may want to get the Timbo Apps replacement. It's a much more reliable Apps for a fraction of the cost. It was developed by a  2nd gen owner on TDR.

 

Most important is to make sure that your turbo is not leaking oil into the intake, causing the runaway situation. It's usually due to worn bearing seals as oil is normally pumped to the extreme high rpm turbo bearings. This can cause a very dangerous runaway situation that can be explosive. Others will chime in with more.

Edited March 21, 20232 yr by JAG1

I thought APPS almost always set a code? The truck never runs completely away, just spikes RPM for a second and comes back down.

I've got a Timbo styled APPS in the store.

 

https://store.mopar1973man.com/dap-commercial-grade-throttle-position-sensor-tps9804.html 

 

As for wild throttle try down the W-T ground wire mod.

 

https://mopar1973man.com/cummins/articles.html/24-valve-2nd-generation_50/51_engine/electrical/w-t-ground-wire-mod-simplified-r574/page/2/?tab=comments#comment-149

 

This might fix it. But have the alternator tested for AC noise.

4 minutes ago, Mopar1973Man said:

I've got a Timbo styled APPS in the store.

 

https://store.mopar1973man.com/dap-commercial-grade-throttle-position-sensor-tps9804.html 

 

As for wild throttle try down the W-T ground wire mod.

 

https://mopar1973man.com/cummins/articles.html/24-valve-2nd-generation_50/51_engine/electrical/w-t-ground-wire-mod-simplified-r574/page/2/?tab=comments#comment-149

 

This might fix it. But have the alternator tested for AC noise.

Isnt the W/T mod for automatic trucks?

 It us beneficial to automatics having shifting and lockup issues. 

 It also benefits manual trucks by eliminating the a/c noise from the equation and also fixes the horrible ground wire splices under the hood and you'll get good clean DC current once it's done.

Awesome. I will try this stuff out and report back

 I would also proceed with the instructions of @JAG1 in checking for an oil leak into the turbo piping. Any extra oil/fuel will cause it to Rev uncontrolled. Eventually it could get to the point of serious damage.

11 hours ago, Doubletrouble said:

 It us beneficial to automatics having shifting and lockup issues. 

 It also benefits manual trucks by eliminating the a/c noise from the equation and also fixes the horrible ground wire splices under the hood and you'll get good clean DC current once it's done.

A/C ripple is damaging to the electronic circuit boards, PCM, ECM, ECU and can cause fluctuations in some cases. Both my second gens seemed to run smoother, noticeable even when running at idle. Before and after tests of the amount of A/C noise reduction after doing the W-T wire harness modifications has shown a significant reduction in the electronic Sadam noise war going on and creates a cleaner signal thru much of the DC  system.

On 3/20/2023 at 7:51 PM, harryslemons said:

I thought APPS almost always set a code? The truck never runs completely away, just spikes RPM for a second and comes back down.

I had a apps that surged like pulling a half load of water when it sloshed forward and back. Then it worked just fine for about 2 months and right back to the same old crap. This went on for a year and never threw a code at all. I was told it could start the run away thing also. New Timbo and no problem since.