Make: Subaru Model: Loyale Mileage: 249,000 Transmission: Auto Year: 1992
Hello everyone
Before the high idle the engine would stall with the ac on. After cleaning the IAC valve the engine has not stalled yet with the AC on. However, about a week later the engine started to surge and idle high. I did find the air filter to have a gaping hole on it (for some strange reason) and replaced it with a new air filter. I also checked to see if any pieces of filter element broke off and entered the engine but luckily all the paper elements remained intact.
The engine no longer surge but the idle is still high (1250 RPM at operation temp). I have checked the MAF and TPS for voltage specs in accordance with Haynes repair manual, unplugged and replugged sensors to hear a change in RPM (I'm guessing that indicated the sensors work), throttle valve moves freely and closed correctly, and carefully checked vacuum leaks with a can of throttle cleaner around the throttle body and vacuum system but no changes in RPM.
I had someone tell me to adjust the idle speed screw but I don't think that's the case since the engine was idling normally before (750 RPM). In fact, it may fix the high idle but will develop problems later.
Any advice? Thanks!
Although no resolution reported, there are some suggestions here, notably the temperature sensor and vacuum leaks:
https://www.ultimatesubaru.org/forum/topic/116735-ej22-high-idle/
That car is too old for OBD2 scan tools, you'd need something that can read Subaru OBD1, or use the blink code method to see if there are any codes:
I checked the resistance on the coolant temp sensor in accordance with Haynes repair manual and it stated that with the sensor cold the value should be between 2k to 3k ohms and with the engine at operating temp, 700 to 1k ohms.
I was getting 16k ohms when cold and 230 ohms when hot. The values are out of spec and got a new part coming in on Tuesday. I will check the resistance on the new part to make sure it's within specs.
Could a bad coolant temp sensor affect idle?
Yes, if the computer thinks the engine is cold it will stay on fast idle.