I have a 95 355. What controls the IAC valve? MAF? Water temp sensors? What controls the increase in rpm when ac on? I have a problem where idle goes to 1500rpm when engine is hot.
I don't know the specifics of the F355 but I can explain how this generally works on most fuel injected cars. The ecu calibration will have a table which has a desired idle speed vs coolant temp. In order to be in idle control (closed loop idle control will adjust air bleed, -idle air control valves- and ignition timing to try and achieve desired speed.) Most common thing I see for an "idle" speed higher than it should be is the pcm receiving a tps input that is above idle threshold. If the ecu thinks your foot is on the throttle, it's not going into idle control. So yes, if your coolant temp sensor was reporting incorrectly (opens and shows negative 38deg for example) it would put the ecu into a higher desired idle, not sure about 1500 however. I would start with checking throttle position sensor values. Lastly, A/C request bumps up idle airflow to offset torque loss to compressor, so if somehow it got an a/c request but the compressor was not engaging (or system empty) idle speed would overshoot. (but this is usually momentary and not a condition that would exist for an extended amount of time)
No car runs great judt the creeping idle. Looking into it this winter. Putting on a dyno this winter and checking and adjusting mixture and other things
Check your idle control valves Over time they can wear into a grovved position Can't remember but I think I run Porsche units. May just want to take them out and try cleaning them and the connection s
Exactly try cleaning them first if the are bad it may correct it temporary. Clean connections also. Very common on this icv design. Not sure on the part number but it's a common crossover number
Idle control valve. Bosch 0280140527 - Volvo Idle Control Valve 92 to 94 960 - NAPA CRB 219490 Best price I could find new at RockAuto.
