2008 H3 Adventure 3.7 I5; engine is out of an '09 GMC Canyon. Idle was about 100 RPM too low which turned the truck into a big vibrating-massage chair, which is great for about 5 minutes then gets old. The original engine idled fine, so I swapped the throttle bodies and now it idles high enough to throw a P0507. The weird part is that it's erratic; on first start it will drop to the normal 650-700, but after driving it will go up to anywhere from 900-1200. If it was constant I would suspect vacuum, if it happened on the old engine I would just replace the IAC (or worse, TPS). If I let it idle after running, it will vary in a way similar to if I was turning the AC on and off in an older car.

I will disconnect the battery and make the ECU relearn with the current throttle body when I get home from work today--and since I have a rebuildable spare I will stop at AutoReilly for rebuild parts--but in the meantime, I thought I'd stop in here and see if anyone's dealt with this. Ideas?

 

Welcome to HF.

Disconnecting the battery will do nothing to "relearn", the PCM stores the last 300 ignition cycles in flash based memory.... power or no power. It can clean up a glitch if any like a computer reboot.

Questions:
1) are you still using the crappy OEM Battery Terminal Connectors? If so, hack them off and replace with a quality aftermarket set like Stingers or your favorite brand. #1 mod to do to every H3.
2) did you clean the throttle body with TB cleaner before your swap? If not, do that for sure.
3) when you started the truck after the TB swap, did you remember to NOT touch the accelerator pedal and allow the truck to idle for several minutes (up to 10 minutes and never rush it) to complete the PCM/TB handshake and response?

Make sure the truck pigtail connector to the TB is clean, spray it with Electrical Contact Cleaner & let it dry. Check the wires to it for cracks/frays etc... Might as well clean the MAF with MAF cleaner while you are at it.

 

Forgot to mention, there really are no "rebuild parts" for these TBs.

 

I did #2 and #3, on both (cleaned the throttle body first on the low one hoping that would fix the problem).

 

If you used Throttle Body cleaner performing #2 that rules that out. If you used carb/choke cleaner, then you need to redo it as that stuff deteriorates the little plastic gears inside the TB and is otherwise bad do do for TBs.

The electrical connection is important, even tiny irregularities can cause issues so definitely clean the connector contacts on the truck and the TB. #1 may help your present issue, but it will definitely avoid future other issues.

Let us know how it goes.

 

You currently have the LLR engine, from the '09 canyon donor?
Why was the original engine replaced?
The worst thing to do is disconnect battery, without a proper relearn procedure.
Btw, GL trying to find parts at "AutoReilly".
Vacuum leak, from what I can make out on your post.
zenoreilly
Zen; a Japanese sect of Mahayana Buddhism that aims at enlightenment by direct intuition through meditation
O'reilly

 

was the new engine flex fuel? if so the injectors are different they flow more fuel. cold engines like alot of fuel. hot engines like lean fuel mixtures and if you reused the throttle-body gasket it might be bad.