Engine/Transmission (1998.5 - 2002) RPM's surge while driving ?

[Dodoro]

I have noticed lately (last 2 - 3 weeks) that the RPM's kinda bounce around maybe 25 - 50 RPM's. I can feel it (seat of the pants)

Cruise on or off.



Was going to clean out the APP's trick this weekend.



Any idea's???

Thanks

 

[PC12Driver]

Probably the APPS. In an auto trans truck the APPS is still used for cruise control (so the PCM will get throttle position information to control shifts - for manual trucks cruise is all internal to the ECM). So if the APPS is starting to get flakey you'll feel it with the cruise on or off in your truck.



You'll probably fix the problem for a little while bit by cleaning it, but odds are that once the APPS starts to get noisy it's worn beyond its usefule life and will need replacement (about $380).

 

[mhenon]

Check this out. With your automatic it might be the fix:Dodge Diesel Rewire Kit

Download the instruction sheet. It looks pretty simple.

Mike

 

[TCluff]

sounds simple but check your fuel filter!

 

[mhenon]

sounds simple but check your fuel filter!

Good point. . do the easy stuff first. Anymore I assume everyone has a fuel pressure gauge with a 2nd gen engine. Almost suicide to run without one.

Mike

 

[Dodoro]

Thanks for all the help. I was afraid the APPS might be going out.

Batteries are 1 year old just did a load test in DEC.

And fuel filter iwas replaced iin Dec. also



Where might I get a good deal on a new APPS?



Thanks again!

 

[Tom W]

It could be your torque converter locking and unlocking. Do a search on this before replacing the Apps.

 

[PC12Driver]

A torque converter locking and unlocking would give a little bigger rpm swing than 25-50 rpm I'd think.



Take the transmission out of the equation. Put it in park and slowly bring up the rpms. The APPS will typically wear first where it spends the most time, in the 1700-1900 rpm range. My APPS was smooth until that range, and then the tach would hesitate and jump (not much, but noticible) for about a 200 rpm window, and then smooth out again above that.



Sometimes you can temporarily clean off the contacts in the APPS by fanning the accelerator pedal back and forth (engine off). Kinda like cleaning the crackles out of a volume knob on an old radio. That worked for me for about 10-20 miles and then I was right back to where I was, but at least it pointed to the APPS.



I ended up getting my replacement APPS from Hoesli Diesel. I haven't looked around recently, but they were very competitive 2 years ago.