Engine/Transmission (1994 - 1998) new (old) truck advice

[tthomason]

Just picked up a 97 12 valve Cummins. I need some help / advice on a problem I'm having when cruising.



My RPM's drop about 200 rpm and then jumps back to where it was then back down again. It comes and goes, sometimes 10 times in a mile and again only once in a few hundred miles.



Doesn't matter if I'm towing or not. It does seem worse in cold weather. Hills or flats make no difference.



Thanks for your help,

It's good to be back again

 

[mikel]

Sounds like the torque converter is locking and unlocking to me. I believe I recall mention of a throttle position sensor or accelerator pedal sensor or something similar to that which would fail and cause these symptoms.



Hope this helps,

Mike



Oops, I looked at your profile, but that's a different truck. Is the '97 an auto?

 

[jimk]

Originally posted by tthomason

Just picked up a 97 12 valve Cummins. I need some help / advice on a problem I'm having when cruising.



My RPM's drop about 200 rpm and then jumps back to where it was then back down again. It comes and goes, sometimes 10 times in a mile and again only once in a few hundred miles.



Doesn't matter if I'm towing or not. It does seem worse in cold weather. Hills or flats make no difference.



Thanks for your help,

It's good to be back again

tps switch, try cleaning with contact cleaner. You can also slot the holes and try to adjust the switch. That would be my first thing to check. lol jim

 

[tthomason]

Haven't posted this truck yet, it is an automatic with 355 gears 4x4 . I do still have my 98. 5, excellent truck!



Thanks for the help, I will try the TPS.

 

[shendren]

the electronic spray is only temporary. i had the same problem for 2 years. dealer can't fix it. the problem is noise in the signal between the tps and the pcm. it's an easy fix. you can permanently fix the problem by rewiring the tps/pcm connection. i have done it to several trucks. scott. -- email address removed --

 

[Dfuruness]

Yep, it is the TPS. I had the same problem 4 years ago.