High idle and idle bouncing

I recently bought a 2001 4x4 2.7 5 speed. Pulled the motor and put a new head on it, timing chain kit and All new seals. I got everything back together and put back in. When the truck is cold it idles smooth but high (2 thousand rpm’s). Once truck is warm it bounces from 1 to 2 thousand rpm’s back and forth consistently. When driving it drives and runs fine. I thought it was a idle air control valve so ordered one off of rock auto and didn’t change anything. Sprayed the whole motor with carb and choke clean to check for vacuum or gasket leaks and didn’t seem to have any. Any idea what the problem could be? I’m lost at this point. Any help appreciated.

 

Any check engine light codes?

mine was idling high when i had egr issues after putting the head back on, but don’t recall bouncing

 

It's possible that the idle will settle down with time while the ECM relearns.

 

I disconnected the battery for a minute tonight after installing idle air valve and reconnected. I’ll see if it changes anything in the morning. I’m not so much concerned with the high idle but the bouncing between the 1 and 2k. It’s as if I have a vacuum leak but almost certain I don’t.

 

No check engine lights.

 

mine was acting similarly with a bad ECT sensor (back of the block), high idle when cold and bouncing. but typically stopped bouncing once it was warm

 

Mine doesn’t bounce until it’s warm. Only high idle cold then warm starts bouncing

 

Drove it to work this morning and pretty much same thing. Noticed it seemed to not have such a wide range when bouncing rpm’s now. Only from about 1500 to 2 thousand rpm’s

 

A dirty MAF sensor can cause issues with high idle or moving up or down nonsensically.

 

This only happens when stopped .

AC compressor cycling on and off

Check the throttle body linkage for hanging up.

I had the firewall crack that made that happen. I only noticed while the truck was stopped never driving.

 

Finally threw a check engine light and says it’s the egr transducer. Going to put one in and see if that fixes it

 

Try a hot soak with some sea foam. It does wonders. You have nothing to loose except $7 for the can if you get it at walmart vs $14 at autozone.

 

Take it apart and soak or just remove it and soak? I’ll try this. Doesn’t seem to difficult to remove so going to swap my brothers on off of his truck to verify it’s this part. Thank you!

 

Just pull a vacuum line and slowly add the fluid. Let it sit for 15 min then run the truck till it burns everything off. Youtube has a ton of these videos.

 

Is there a better vacuum line to pull to run it though if I’m mainly focusing on egr?

 

I think it depends on ur motor. On my 3.4 I just pull the line off the brake booster.

 

Put a new egr valve on and it fixed the idle bouncing problem stays at a steady high idle now. Now the idle is higher and stay right around 2600 rpm’s consistently. Egr vacuum motor or vacuum solenoid? Or temp sensor on back of motor? Thoughts

 

I'm in a similiar boat. Idles 1500-2000. slowly climbs to 2000 and then drops to 1500 or so after a few minutes and climbs again. Drives fine, but when coasting in neutral, it bounces between 600 and 1500 or so I think, then settles back up to the high idle when stopped. Just wierd. Did you do anything else to yours? On mine, I had deep cleaned the intake, deleted EGR, deleted Cats, added street headers and CAI. Also replaced the various valves in the evap vacuum lines. So you might be like, well no wonder yours is acting wierd lol. Well I figured it was just trying to relearn itself and would settle down. Probably driven about 75 miles in it that way so far and its still doing its thing. Hopefully it won't have any negative long term effects. I haven't done a vacuum check on it, but meant to. Probably will this afternoon. Following to see if you figure anything out.

 

Bouncing idle almost has symptoms of throttle position sensor. Any way to try a different tps to rule that out?

 

Put a new egr valve on and it fixed the idle bouncing problem stays at a steady high idle now. Now the idle is higher and stay right around 2600 rpm’s consistently. Egr vacuum motor or

it’s not bouncing anymore fixed that problem now just really high idle