I have a 92 Corolla with a persistent high idle. When first started cold, it only idles about 1000 RPM. Then as it warms up, it will increase to about 1400 RPM and when completely hot, idles at 1100 RPM. I've double and triple checked all vacuum lines for cracks and checked everywhere for vacuum leaks and found none. All vacuum lines have been doulbe checked for proper routing and location. I've changed the thermostat with a new one from the Toyota dealer. I changed the coolant temp sensor, and incoming air temp sensor in the air box with known good ones and even swapped computers with a known good one. The idle screw is all the way in, and it is still idling higher than it should. Any suggestions on what to try next?
Don't know if you wrote in error, but when you turn the idle screw in/ clockwise, it raises the idle. Vice versa for counter-clockwise.
Could be a sticky/ dirty choke.
Your fuel mixture may be set too rich or something fuel-related in the carb is slightly worn.
I hate my carb, btw, in every aspect. Been through several of them. Right now, mine idles between 1100RPM to 1500RPM.
Thanks for the information but a 92 Corolla is fuel injected, not carburetored, thus, no choke to deal with. The idle screw in the throttle body when turned in clockwise, is supposed to limit the air entering the engine, thus lowering the idle.
Give your IACV a good clean. You'll have to take your throttle body off, flip it over, undo the four screws, and clean it thoroughly. They occasionally get caked with carbon built-up and can cause problems with your idle. Adjusting the idle screw is basically a waste of time, as the idle is controlled by the ECU. I wanted mine to idle slightly higher, so I put a nut on the end of the idle screw, which worked for a couple of hours, until the ECU automatically tuned itself back to where it should be, lol.
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Give your IACV a good clean. You'll have to take your throttle body off, flip it over, undo the four screws, and clean it thoroughly. They occasionally get caked with carbon built-up and can cause problems with your idle. Adjusting the idle screw is basically a waste of time, as the idle is controlled by the ECU. I wanted mine to idle slightly higher, so I put a nut on the end of the idle screw, which worked for a couple of hours, until the ECU automatically tuned itself back to where it should be, lol.
The problem was a stuck IAC Valve. I swapped the throttle body with another spare I had and it now runs perfectly. Thanks for the information, Kiwi.
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1993 Toyota Corolla
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