While I am on the Interstate (70+ MPH) I notice my RPM's jump up about 100 or so! The truck acts like I tap the go pedel then let off and the RPM's go right back. It only lasts about 1 sec. but does it often with cruise on and off and A/C on and off. None of the gauges seem to change when this occurs. Any suggestions??? Thanks

 

Sounds like torque convertor locking and unlocking to me. Is it doing it on flat grades or going up step sections of road?

 

May be ac compressor cycling may be low 134

 

Could also be the TPS sensor, or Vp44. What fuel pressure are you running??

Rick

 

It does not seem to matter the grade. Most is fairly level though.

 

FWIW. I have noticed outside the truck while it is running w/ AC on, I hear the compressor cutting on and off often! But my problem seems to exist with and without the AC on.

 

TPS= Throttel Position Sensor???

Please don't even mention VP44 problems I sure hope not anyway!!!

FP= 13-13.5 Idle
9-10 WOT



Thanks all for your suggestions and help!!!!!!

 

Looks like your FP is ok!

There is a thread on here regarding insulating the wire going to the TPS with tin foil but I cannot find it. From what I remember of it you wrap tin foil around the wire going to the TPS from the alternator to 6-8" past the alternator and then wrap it in electrical tape.

My other options would be to check all of your ground straps for good connection, and check your battery cables for corrosion. Make sure that you check all the pigtails coming from each battery also. The battery cables should not have more than 1 ohm resistance per foot of cable. (Please disconnect them before checking with ohm meter).

It's possible that your pcm is getting the wrong signals via low voltage from anyone of a dozen different sources.

Stupid me is this a 12v or a 24 valve??

Rick

 

I'll bet it your torque converter slipping in & out of lock... my '98 did it from new 'til I replaced the tranny last year and wired in the "mystery switch"