High Idle Help

[EricBirk]

Hey guys,

I am hoping to head out with the truck this weekend on a trip and seem to have developed a bit of an idle issue...

I have a 2002 DC 3.4L auto. Cold or warm it idles at around 1,500rpm in neutral or park. Driving down the road @ around 70km/hr if I step off the throttle the engine idles down to around 700, then bumps back to around 2k and holds. While that happens you can actually feel a bump as it revs back up.

The idle is high but smooth, it drives fine, gas mileage has not changed.
I changed the TPS only to put the old one back on as it didnt fix the problem. Also removed the TB and IAC, cleaned both, and checked the resistance and function of the IAC. Assuming with no power it sits about 10% open, then when the key is turned on it closes, then it checked out. As per the service manual I also unplugged the air assist hose and plugged it. The truck slowed down to about 800rpm but didnt chug or stall out.

Also checked all vacuum lines, and even drenched the engine in TB cleaner with no effect on idle.

Had it hooked to a Snapon scanner and at idle it showed a 9% throttle opening, hence why I changed the TPS. That didnt change a thing...

I am at a complete loss, someone please help.

 

[mmtoy]

Have you checked your temperature sensors/thermostat? If it's idling high it *may* be because it thinks the temperature's still low due to a faulty sensor or due to a bad thermostat. I'm just throwing this out there--I'm not terribly familiar with the 02 Tacoma.

 

[EricBirk]

Have you checked your temperature sensors/thermostat? If it's idling high it *may* be because it thinks the temperature's still low due to a faulty sensor or due to a bad thermostat. I'm just throwing this out there--I'm not terribly familiar with the 02 Tacoma.

Good idea to check.
However, I did solve the problem today!!! FINALLY!!!

A bit of maintenance, and a bit of my own stupidity unfortunately...

A few weeks ago I developed a bearing squeal and in the process of loosening off the belt's to figure out what it was I unplugged a connection to the power steering. That was definately part of the problem. The other was just a dirty IAC, and the throttle plate needed to be aligned as it was getting caught on a wear mark on the throttle body.

All is good, now to change that CV boot that I ripped...