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Re: Idle Control Valve (NOT?)

> > applied voltage to the sensor is about 1.7V.  The Haynes manual states 
> > the sensor's thermistor should produce 2100-2900 ohms when cold and 
> > 270-400 ohms when warm.  Although the resistance reading is too low 
> > when cold, it is within the correct range when warm.  Therefore, when 
> > the engine is warm, I cannot attribute the fast idle to the sensor. 

I agree with this - your temp sensor is not causing your fast warm idle.

> > 3. Resistance across the valve terminals should be between 9 and 10 
> >    ohms.  I received a reading of 10.6 ohms which seems close enough. 
...
> > 5. An ammeter placed in series with the valve should read 400-500mA at 
> >    idle. It reads 560mA at 1600 rpm but will drop to within specs when 
> >    I reduce the idle by pinching closed the hose from the valve to the 
> >    intake manifold.  It seems that the control current is correct. 

Taking these two together, it sounds to me as if there may be something else
wrong (as well as possibly something wrong with the valve). The resistance
reading is high. What kind of confidence do you have in the zero setting
on the ohmmeter? And how confident are you in the contact you were making to
the valve terminals? These two factors could easily lead to an error of 
0.6 Ohm.  However, if the resistance reading is accurate, then I would expect
less current for a given control voltage, not more, as you have measured.
However, this is not too indicative, since the controller may be upping the
control voltage in an attempt to force the idle down to where it should be.
Anyhow, I would be very tempted to try to borrow a known-good idle control
valve to see if installing it helps. I had the opportunity to perform this
repair recently (the manual, in three separate places, indicated that the
idle control valve was the culprit for the symptoms I was seeing) but I
persisted in investigating after finding out the price of one of those
buggers. It turned out that there was an intermittent bad ground in one of the 
fuel injector wires, the repair of which cured the problem. I would have been
Very Upset if the (non-returnable "Oh, that's an electrical part, electrical
parts are NOT returnable") $170 ICV had failed to improve matters.

> > By the way, the oxygen sensor is putting out the correct voltage, I've 
> > found no vacuum leaks, and the timing centrifugal advance is operating 
> > normally. 

Try to verify good connectivity and good contact end to end on the control
wires. This may require fabrication of a couple of test connectors, but
at the price of avoiding an unnecessary ICV purchase, this is pretty
cheap and may come in handy at a later date...


- -- 
- ---
John R. Lupien
lupienj@domain.elided