Re: Seeking Idle Control Unit for 1986 5kcstq

["Scott M." <scottmo@teleport.com>]

Douglas,

If you have already cleaned out the ISV valve, I would
recommend that you
take the idle/full throttle switch off the car, (mark its
position) cut open/off the plastic cover, resolder the
cracked internal solder joints near the connector for the
idle and full throttle switch contacts. Then check if your
idle behavior is back to normal. While it is possible that
the idle stabilizer control unit is defective, every
throttle switch I have opened up on these 86-88 5000TQ cars
was intermittent due to cracked solder joints. This causes
the idle speed to go up and down at random times, sometime
tapping the throttle gets the idle to come back down.
Sometimes when you test the idle switch it will test fine,
the next time high resistance/open circuit. The same is
true for the full throttle portion of the switch.

BTW: if you remove the connector from the ISV valve with
the engine running the idle controller will turn off the
ISV valve when it senses an open circuit. You need to turn
off the engine and restart after reconnecting the ISV valve
to get it to start functioning again.

You may also want to check the temp sensor at the top of
the cylinder head water outlet, this is the one the idle
stabilizer relay uses to sense engine coolant temps. Remove
the single wire and check the sensor for ~1000 ohms at
68Fcoolant temp or ~130 ohms at 176F. You may also want to
pull the fault codes and see if anything else is amiss.
Check the Bentley manual for details, if you don't have the
Bentley, buy one ASAP.

HTH
Scott M.
----------
> 
> Engine idles high, oscillating between 1300 and 1400 rpm.
If I
> disconnect the idle stabilizer valve, and then plug it
back in,
> it settles down. (I saw this discussed many times in the
archives).
>