Engine/Transmission (1998.5 - 2002) APPS Problem?

[MAYoung]

Gentlemen:

I have a 1998.5 2500 4x4 with a NV4500 5-speed manual. Truck is pretty much stock except for a DDRP and a three gauge setup on the a-pillar. The symptoms are this:

When I am driving at speed (60-70 mph) without using the cruise control, I will experience a subtle drop-off in RPM's that will require me to adjust my foot-pressure ever so slightly. It is not a huge change in RPM or speed, maybe 5 mph at most, but it is noticeable. When I place the engine on cruise control, it does a better job in chasing the drop-off in RPM's but it is still present.

Other indicators are normal. Fuel pressure remains constant, ammeter needle is steady, engine temp is rock steady. No error codes. I spoke with the Dodge dealer locally,decent local operation, and they said it may be the APPS. I replaced the APPS unit three years ago (September 2012). The fuel filter is new.

I am open to suggestions as to troubleshooting as well as hoping to learn if anyone has encountered a similar problem.

Thank you in advance.

Mark Young
Fair Oaks, CA

 

[klcammie]

is tach steady? Check connections to Vehicle speed sensor on rear axle. Check and clean grounds like the one on pass. side batt. Check and clean the connection for the APPS. One other check the vacuum lines under Driver side batt. tray for corrosion or breaks. These are what I did for my 01.