Hi,
My mpi has been idling badly for some time - at times it seems ok and at other times the revs are too high at about 1200-1500 but not as high as some posts I've seen in here. I'd say it always seems ok when cold - the revs are higher as expected but once full warmed up it doesn't always drop to below 1k. I've read a lot of the other posts on what seems to be a fairly common problem but I still have a few questions:
1) On a healthy setup, how quickly should the revs die back to idle after you blip the throttle? Say I blip the throttle to 2-3k and then take my foot off. The revs seem to quickly drop off to about 1500 and then there is almost a pause before they drop more slowly to normal idle speed (when it is idling normally) - is that expected behavior or should the revs drop almost immediately to idle?
2) After reading various posts here I stripped down the throttle body and idle control valve and cleaned both thoroughly. This does seem to have improved things but I'm not entirely convinced. One thing I noticed when I had the throttle body off the car is if you hold it up to the light you can see a glimmer of light around part of the circumference of the throttle blade when it is closed. I actually have two throttle bodies and they are both the same in this respect - we're not talking much of a gap but enough for light to get through. Is this normal or when the throttle is shut should it seal completely? I've read about warping etc but don't know how severe that is and the fact two bodies are the same made me think maybe it's not supposed to be a perfect seal?
3) I've seen that there was a mod issued for the water temp sender which can have some influence on idle. - I assume this was just to alleviate any pulling on the harness which is quite tight? If I remove the connector when the engine is running the fan comes on immediately so there is clearly a signal there. Is that a good enough test?
4) Does the oil temp sender have any part to play in the engine management or is it just there for the gauge? I believe it is routed through the ECU but I don't think it is an active control signal. My gauge hardly moves so I suspect there may be a sensor issue hence my question.
Any help or suggestions appreciated?
Thanks, Jeff