Hey guys I was wondering if I could get a little help here. So I have an 02 Montero Sport Limited and I've had this problem for a few months now. It seems to want to idle around 500RPM when the engine gets hot and in drive. It hasn't ever completely died on me yet, but it does seem to want to. I did some research and found that a simple cleaning of the throttle body and plate is a common fix for this problem. Well, I cleaned my throttle body and plate and didn't disconnect my battery (just to see if the idle would maybe be higher) and I added seafoam through the engine via the PCV pipe and into my crank case and gas tank. Even after all this crap it's still idling around 500RPM!

Some weird notes about it;
-It won't idle that low when the car's cold, only when the engine is completely warmed up.
-It only wants to idle under 1,000RPMs when my headlights are on. I've noticed when I turn them on and off, or even when I have my back window defrost on it'll make it want to idle lower and lower when it's in drive.
-When I do turn the headlights on and it starts to idle low if I turn the window defrost on as well or mess with the windows it'll cause my headlights to dim and all my interior lights to dim until I hit the gas and everything brightens back up.

From that last note I thought it could be an alternator thing. But I'm not sure this is the case because I figured the lights are dimming simply because the idle is so freaking low.

Anyone have any suggestions to fix this really annoying problem? I had a mechanic tell me it could be my O2 sensors, but from the symptoms I thought the throttle body cleaning would just fix this crap...

 

I am having the same problem that you posted last year. Did you ever find out what the cause was? Your help would be greatly appreciated!

 

Faulty O2 Sensors.