Cleaned Throttle Body - Now High Idle

[ubermoto]

So I've been struggling with this issue for a couple months now. I was getting pretty poor fuel economy so I cleaned the throttle body and ever since it has been idling high - like 1700-1800 rpm.

After that, I've tried just about everything listed in the FSM:


Sprayed brake cleaner around hunting for vacuum leaks - found none.
Tested resistance of TPS and IAC - both are within spec.
Removed IAC and tested with 12v battery - opens and closes fine. Used RTV to seal up IAC gasket mating surface.
Unplugged TPS while engine was running then plugged it back in
Cleaned MAF meter
Tried adjusting dashpot piston/locknut
Tried adjusting throttle opener piston/locknut


So lately I've mad a few more observations:


If the throttle valve is allowed to 'slam' shut (i.e. goose the throttle) when you are coming to a stop, the idle will drop to around 1100-1200 rpm.
If I stop and it's idling high, I can turn the engine off, then start it back up and it will idle pretty normal around 1000 rpm.


I haven't had a chance to get out and experiment with it recently since its been snowing.

Thanks for any ideas guys...

Cheers,

Jeremy

P.S. It's a 97 Taco with the 3.4l V6 and about 200k miles...

[CJM]

I cannot remember who it was, but I want to say they replaced the throttle body in the end to solve the issue.

[j-money$$$]

I cannot remember who it was, but I want to say they replaced the throttle body in the end to solve the issue.


maybe you are referring to my post on yotatech about this. I got a throttle body from a pick a part and fixed it. i was posting a thread about that for months. it took my forever to fix it and that was the only fix


I did the same exact thing you are explaining. i cleaned my throttle body for the fist time of my knowledge around 200k miles. after i could never get the idle to come down.

Try physically shutting the throttle body when its idling. You have to close it pretty hard. So rev it up through the throttle body and shut it too. just twist it back extra hard.
this should return the idle to normal. if this works my guess is the butterfly valve is slightly warped or something. My only guess is that carbon forms and it seals but once you clean it it wont seal. Causing this idle to go up

good news>>> used tb's from pick a parts are about $40
bad news... you have to find one haha


goodluck

[MTL_4runner]

Here's the thread where the TB needed to be replaced:
http://www.ultimateyota.com/index.php?option=com_smf&Itemid=26&topic=8109.0

I have seen the IAC stick and cause high idle. The cure for that is to simply remove it, soak it in PB Blaster and then reinstall it again. If the idle still doesn't return to normal you may need a new IAC and or TB.

[BruceTS]

I had the same issues with my TB after cleaning it too... What I discovered was the linkage wouldn't completely close after letting off the throttle. I lubricated the piss out of it and it didn't help. After readjusting the throttle damper thingy, I got it to somewhat working properly. Long story short it's working fine now, but took a few years of a funky idle. Never gonna clean my TB ever again.....lesson learned.

[MTL_4runner]

I had the same issues with my TB after cleaning it too... What I discovered was the linkage wouldn't completely close after letting off the throttle. I lubricated the piss out of it and it didn't help. After readjusting the throttle damper thingy, I got it to somewhat working properly. Long story short it's working fine now, but took a few years of a funky idle. Never gonna clean my TB ever again.....lesson learned.


I'm surprised to hear that Bruce because I've had trouble with the IAC sticking after being cleaned but never had any issues with the linkage or the butterfly valve sticking inside the TB. Could it have been excessive wear perhaps causing it to catch on the inside of the TB bore? Not sure why adjusting the throttle damper would help the situation unless it was maybe catching at a specific place and backing off the damper changed it enough to help that situation.

[BruceTS]

the linkage was sticking just enough that it wouldn't completely close. I could push with my finger and make it close the rest of the way, after tearing it apart many times and lubricating everything, I decided to back off the damper. This helped greatly in allowing the idle to drop, but if I slowly let off the throttle it would still run high, I used to have to tap the pedal quickly to make the idle drop. About a year ago it finally started to act normal again. I could never figure out exactly what was causing the sticking problem, even thougth about adding another return spring. Now I only clean the bore with a dampen rag when ever I have the intake tube off, no more spraying the whole thing out.

Each time I sprayed out the TB, it usually took a day or 2 for the idle to drop back down, but doing the complete clean out really messed things up :bangdesk:

[corax]

You probably washed varnish into the throttle plate bushings, pull the throttle body off and give it a really good cleaning. Pull off the TPS and spray the t-plate bushings clean. If you have one, remove the throttle damper thing and give that a whirl also.