Does it do it all the time, or just after the truck is warmed up? Is it running hot at all? I assume the CEL hasn't come on, allowing you to pull codes? When the truck is cool, pop the radiator cap and check your coolant level. Usually if the coolant is low, though, it will bounce back and forth like that constantly after the truck is hot.... and won't stop when you rev it up.

Beyond that, cracked/broken/disconnected vacuum lines will mess up your idle. Good luck <img src="/forums/images/graemlins/kewl.gif" alt="" />

Sean Strawmyer
Back and ready to rock...... crawl.

From Indiana or surrounding states and interested in wheelin'? Check out www.mwior.com