High Idle after Drive Belt Change

[North]

Hi guys,

This weekend I changed out the PS and AC belts on my 99' 4runner (V6). Toyota dealer sold me the wrong alternator belt, and then Napa did the same thing, so I couldn't replace that one.

Belt squeal during startup was cured, but it did sound like there was a bit of drag somewhere in the system.

Drove 50mi yesterday without issue, drag noise seems to have quieted. This morning I start up and halfway through a <5mi drive my rpms are super high. 2000 at idle and closer to 2500 when I first push the clutch in. Same thing on the way home (noticed it immediately this time). Could the belt tensions be affecting this in any way? I never found a great method for making sure they're correct. Alternator tension should be the same since I marked the adjuster bolt, but could a tight AC or PS belt be contributing? I did remove the airbox to get at the PS adjuster but I'm 99% sure I re-attached all hoses (only had to pull 1).

Any ideas?

 

[shadow247]

That seems pretty odd, since the belts don't really affect the way the engine runs. I suspect your high idle is caused by something else. As far as how to test belt tension, I found this tool at Rockauto - RockAuto Parts Catalog

 

[nevada]

probably a vacuum leak.
recheck all the hoses, and connections.

 

[North]

Checked all hoses and tightened the clamps on 2" hose from the airbox. Didn't find anything unusual.

Haven't had a chance to drive it again, but started it up this AM and it starts at about 1800rpm, and then stays steady around 2000rpm once warmed up.

 

[LittleCaesar]

How much deflection did you allow in the new belts? But I agree it sound like a vac leak.

Check your butterfly valve to make sure it is closing all the way.

 

[North]

1/4" for the AC & PS, 1/2" for alternator. That's what I was aiming for at least.

 

[LittleCaesar]

Still sounds like a vacuum leak, or something got unplugged.

The deflections of the new belts are OK.

 

[North]

Update:

I spent weekend 2 searching for vacuum leaks and doing a 'quick clean' of the IAC as suggested by a poster on yotatech. This involves spraying MAF cleaner into the IAC port (small square hole at the bottom of the throttle body) with the truck running. No vaccum leaks found, idle was still high.

Took the truck into the local shop on Tuesday for their opinion. They suggested IAC valve replacement ($280 part!).

Did some frantic searching for other solutions. I wanted to make sure I had tried EVERYTHING before shelling out for a new IAC valve or trying to clean it. Thanks to some good posts on yotatech (by brian2sun) I fixed the high idle by replacing the ECT (engine coolant temp) sensor. $30 part and the truck is running great again!

 

[TOPSECRETTUNDRA]

Thanks for the update. I'm sure this will someday help someone with a similar issue.