Having troubles with my '89 4Runner - 3.0L V6, Auto, 175K. Idle speed has jumped to ~1600rpm (~1000 in gear) and stays higher than normal while driving and there are occasional stumbles while driving (like fuel or spark has been interrupted momentarily). Sometimes the rpm's drop to 300 or 400 then go back to about 1500 in a repeating cycle. This only happens when in Park or Neutral and I press the brake pedal. The same thing happened once before and I traced this problem to the brake light switch (can't explain what was happening though). I played with several things to correct the high rpm's, including unplugging the cold-start injector, cleaning and resetting the TPS, and resetting timing. Something worked, but only for a couple of weeks. I put match-marks on the TPS body and distributor housing when I finished last time & neither has moved. Anyone got any ideas? Thanks!!!

Sorry itÆs taken so long to get back to this, but IÆve been busy. I think IÆve traced the idle problem to a leak in the AS Reed Valve (aka PAIR Valve), but IÆm not 100% sure. Does anyone know if this part can be tested without taking it off the engine? IÆm pretty sure IÆd have to bust the nuts off of the manifold to get it off. I checked and cleaned the TPS again and spent a lot of time moving it micrometers one way or the other to get all of the settings as close to the middle of the range as possible. I checked the throttle body again and couldnÆt find anything out of whack. Same for the air intake. Checked all the plugs and wires and theyÆre fine. CouldnÆt find any other vacuum leaks. Plan to replace the cap & rotor this weekend. (FYI one of the local dealers has one (1) Factory Repair Manual left for the Æ89 4Runner û only $30. See http://www.longmonttoyota.com/ for contact info.) I may try to do the brake light / ECU bypass just to avoid any future problems. Anyone ever tried bypassing the ~1500 rpm fuel cut itself?

Try turning down the idle. I had a similar problem when I bought my 4Runner. It was idling high and sometimes the rpm's would fluctuate when I pressed on the brakes.

To fix the fluctuating rmp's, you need to turn the idle speed down to about 700rpms and see if that fixes the problem before you start replacing parts you don't need to.

Here's the web page for better detail of the problem if indeed it is your problem. Hope this helps. Good Luck
http://www.geocities.com/toyotashawn/bizzareidle.html