Low Idle Speed

[Guest]

Greetings to all....<BR> A quick question for all that are in the know..<P>I understand that the normal Idle speed on my 88, while in gear, should be 625-650. The problem that I'am having, is when I'm parking and in the process of turning the steering wheel, the RPM's drop to about 550-575, and it feels like it wants to stall. At that time, I can feel the IAC kick in to raise the Idle speed. I just replaced the IAC and the Power Steering Pressure Switch is giving the correct signal to the ECM. Any Idea's?<P>Thank's in advance.....

[Guest trofeo73]

You could check the Throttle position sensor. Change the fuel filter too while your at it. Check the ecm data readout, a service manual should have all the nominal readings.

[bigrog]

The first two things to inspect here are state of tune, and proper minimum air rate. A third possibility is weather related fuel volatility compatibility. A fourth possibility, but doesn't seem to fit the circumstances, that affect idle control is a/c compressor cycling. Make sure the climate control is off next time you duplicate the condition to remove this possibility. <P> The most likely maintainence/age related thing that will cause this is carbon buildup in the throttle bore, which causes improper minimum air rate. Phisically clean(with a toothbrush and brake/parts cleaner if you have to) the throttle plate. If there is too much buildup here(and you would be surprised at how little is too much) the IAC will be operating at a flow value that is never intended to accuratetly handle that much airflow, thus the erratic idle. Best thing to look for is an IAC value of 10-20 counts at hot idle(195*f thermostat), all accessories off. If you command the IAC closed with the output functions, minimun idle speed(minimum air rate) should be about 500 rpm. <P> In short, ensure proper tune-up(mainly filters and spark plugs), then watch for proper IAC values at idle. If all that's good, try different grades/brands of fuel.<P> Your fail conditions suggest open loop operation, and that combined with your region and the onset of winter make me strongly suggest the fuel volatility thing, but it is well worth the time to inspect the throttle body for proper calibration. Again, this is all assuming proper tune-up status. My stated IAC values are assuming proper pcv function and clean air filter.

[Matt]

Did anything ever come from this thread?

[Ronnie]

I would be surprised if anyone is still here that would know.