Lately, my truck has been pretty weird with the RPMs. When I idle, it often will jump up to 1000 RPM while it idles, then it'll fluctuate within a range of 500 RPMs. The worst part is that when I'm driving on the freeway, even on level freeway, and I'm around 60 MPH, it'll jump from 1500 RPM to 2000 RPM and on a frequent rate too. When it does that I can definitely hear it do that. It sounds like I'm slamming on the gas and letting go and jamming it again.
If anyone can help or has had the same problem, it seems like its a bad thing. I'm driving from Los Angeles to Austin, TX in a week and a half, so I think i should get this fixed pretty quick. Thanks anyone if you can help.

 

if the problem was with idle only, it would probably be the IAC.
but since its while driving, i'd guess TPS. about $40-50 at local auto parts.

edit... the rpm jumps you see on the freeway are likely this series of events... the torque converter unlocking, then a transmission downshift from OD to Drive, then torque converter relock, and then finally transmission upshift from Drive back to OD. mine did that and new TPS helped it a lot. mine will still do it occasionally while climbing a big hill, but not all the time like it was doing.

 

I had this same problem but the jump was only 300 RPM's. Let me guess, on the highway, the RPM's jump when cruise control is on.

I had basically everything fixed before the real problem was identified... carbon. Here is how my mechanic fixed it:

1. Extra heavy dose of fuel injector cleaner in tank.
2. Clean the trottle body extreamly well with a good spray cleaner - take it off if you have to.
3. Get OMC outboard engine tuner (what my mechanic used - others hear preffer Sea Foam Deep Creep). Spray the whole can of either product into a fully warmed up engine; turn it off and let sit for 6 or 8 hours. After the wait-time, idle the engine for 15-20 minutes so all the white smoke disapears. Then go for a hell ride on the highway to make sure everything is cleaned out.

I started doing this every year as preventitive maintenance... haven't had the problem since. Should cost no more than $20-$25. Good luck.

 

Thanks guys for the awesome tips. On the second one, it does happen when cc is on, but it happens with it off as well. Thanks again though, I'm gonna try both.

 

Change your TPS (Throttle Position Sensor) - that should fix the rpm fluctuation problem when you drive. The idle problem is probably a dirty throttle body. Somewhere on here is a thread with directions on how to thoroughly clean it. I'm at work, don't have time to find it. If cleaning doesn't work the Idle Air Control motor (IAC) is probably bad.......