mt4runner

During the last couple of months, the idle speed on my 4runner has been slowly increasing. This is apparent at cold start and continueing at operating temperatures. At cold start, it used to idle at 1200-1400 rpm, and settle down to 600. Now cold start is 1700-1800 and warm idle is 900-1000.
Any ideas as to where to start looking would be appreciated.
Regards, Rick

Wheelingnoob

I'm having a similar problem but mine is at 200rpm all the time. If I turn it off and start it when hot it will hold a good 800rpm idle till I hit the gas if I hit the gas right back to a 2000rpm idle. I'm going to look at the TPS and the throttle to see if its sticking, also going to look at the dash pot as well.

Fishaa

I just asked this question in another thread. Everyone was suggesting the IAC Valve (Idle Air Control) and to check that your coolant level is topped up. Mine wasnt quite full and i topped it up and it sorta went away but it also got much warmer here so I still think its this IACV

https://www.yotatech.com/forums/f116...ps-set-224525/

sb5walker

Since your idle speed is dropping when the motor gets hot, the AAV is working. Suggest looking for vac leaks with an unlit propane torch or starting ether, listening for increase in idle speed. You have tried adjusting the idle speed screw, right? BTW hot idle on a 3VZE should be 800.

Vac leaks can be tough to locate. You have to check all vac tubes/hoses and joints in the throttle body/plenum/intake manifold, including brake booster & PCV hoses.

mt4runner

sb5walker, I havn't tried adjusting the idle screw yet, can't see how it would slowly come out of adjustment like this. If the throttle plate (butterflys?) is dirty and not resting at the correct position at idle, would that cause this issue? Would it fool the IAC and cause it to give more throttle at cold start than normal?
Rick

sb5walker

If the o-ring around the throttle adjust screw was old, and it dried out and shrunk, then vibration can cause the screw to move. In which case a new o-ring is in order - get one from any auto parts store. Doesn't have to be any exact size, just one to fit the screw.

I guess a filthy throttle plate could affect idle speed, if there were enough gunk to keep it from closing. Good to check. It's not going to "fool" the cold idle up valve, there's nothing to "fool". The AAV is just a thermostat-like valve that closes the cold idle air bypass when hot coolant hits it. Since idle speed is going down when the motor gets hot, like it should be, it sounds like the AAV is closing just fine.

mt4runner

Just went out and tried looking for the idle adjustment screw. I could only find a couple of screws that I would call Idle stop screws. No rubber o-ring, just a lock nut w/yellow paint showing me that at least these two screws havn't moved. Where is the idle speed adjustment screw located?

sb5walker

A forum search of '3vze idle screw' gave this thread: https://www.yotatech.com/forums/f116...-screw-196596/

The stop screw should never be adjusted.

mt4runner

Thanks, I'll check it out.

mt4runner

Had to go to town today(40 mi.) and it idled fine, both at start-up and after it warmed up. Go figure. Did a vacume leak test, nothing happening there. So I guess I will test the IAC and TPS and make sure they are in spec. sb5walker, if the o-ring were bad on the idle screw, wouldn't that be a potential vacume leak as well? I'm kind of ruling that out seeing how it idled fine today.
Rick

sb5walker

Yes, the idle screw could cause a very small vac leak, but probably not enough to notice.