I am trouble shooting a recently acquired 1995 T100, 4x4, 5vz-fe with a high idle (1350rpm)
Ive performed test from the factory service manual to confirm proper operation of the MAF and the TPS. I pulled the throttle body and IAC and after cleaning them, the IAC also passed resistance and physical open-close test outlined in the factory service manual. I've checked the IAC Valve circuit on the ECU and it passed. The Engine coolant temp gauge also is working correctly based on OBD2 observations. The truck idles up to 1750rpm on cold start and drops to 1350rpm when the ECT gauge reads 180 F. The throttle body valve is closing all the way based on physical observation and 9.4% according to TPS.
Ive checked for vacuum leaks. Found none, but replaced any questionable vacuum lines anyway.
In desperation, I pulled the motor/magnet off of the IAC while the truck was idling. nothing happened. I manually turned the IAC Valve shaft and was able to close the valve off so the truck nearly stalled before I opened it back up. I turned the shaft so that the truck was idling at 750rpm and it set there at 750, but when I shut the engine off, reinstalled the IAC motor/magnet and took it for a test-drive it quickly when back to 1350rpm at idle.
So, why would the IAC Valve open back up and idle the engine at 1350rpm when based on physical manipulation in could close off the airflow and idle correctly???
Could this be caused by a bad impute to the ECU (O2 sensor, AC Idle up circuit) that just isn't producing a code for some reason?
Any Ideas?
I read on another forum that it could take days of driving for the ECU to "relearn" the engine's needs, so my next move is to just drive it around and hope it fixes it's self. haha
Ive performed test from the factory service manual to confirm proper operation of the MAF and the TPS. I pulled the throttle body and IAC and after cleaning them, the IAC also passed resistance and physical open-close test outlined in the factory service manual. I've checked the IAC Valve circuit on the ECU and it passed. The Engine coolant temp gauge also is working correctly based on OBD2 observations. The truck idles up to 1750rpm on cold start and drops to 1350rpm when the ECT gauge reads 180 F. The throttle body valve is closing all the way based on physical observation and 9.4% according to TPS.
Ive checked for vacuum leaks. Found none, but replaced any questionable vacuum lines anyway.
In desperation, I pulled the motor/magnet off of the IAC while the truck was idling. nothing happened. I manually turned the IAC Valve shaft and was able to close the valve off so the truck nearly stalled before I opened it back up. I turned the shaft so that the truck was idling at 750rpm and it set there at 750, but when I shut the engine off, reinstalled the IAC motor/magnet and took it for a test-drive it quickly when back to 1350rpm at idle.
So, why would the IAC Valve open back up and idle the engine at 1350rpm when based on physical manipulation in could close off the airflow and idle correctly???
Could this be caused by a bad impute to the ECU (O2 sensor, AC Idle up circuit) that just isn't producing a code for some reason?
Any Ideas?
I read on another forum that it could take days of driving for the ECU to "relearn" the engine's needs, so my next move is to just drive it around and hope it fixes it's self. haha