Idle Switch Question

[Huw Powell]

> I've been troubleshooting a high idle problem on my 1988 5KSQ (CIS-E III)
> for what seems to be ages now.  Just came in after an afternoon out in the
> driveway with the multimeter and the Bentley.  Some questions wrt checking
> the idle switch (Bentley pp 25.106 and 107).  I suspect this switch, but my
> test results don't follow the Bentley.
>
> No matter how I adjust the idle switch, I get 3.5 ohms between terminals 1
> and 2 with the throttle fully closed.  The Bentley calls for zero ohms.
> Once the throttle moves a wee bit, the resistance changes to infinity
> (open).  This latter measurement is in agreement with the Bentley.

3.5 ohms when closed indicates dirty contacts inside the switch, or poor
contact somewhere between your meter and the harness.  Try making sure
you can actually measure zero ohms accurately on a piece of wire as a
"standard".

>  The Bentley
> states that the fix is to adjust the switch.  The position of the switch can
> be adjusted in its bracket.  But no matter how I adjust it, I still get 3.5
> ohms.  I tried at the extremes of its adjustments - still 3.5 ohms.  Note
> that the Bentley doesn't say to replace the switch.  The fix given is to
> adjust the switch.  BTW the full throttle switch portion checks out OK.
> What am I missing here?

see above, if you can't clean the switch and get it to zero, replace it.

Also - test to see if it's "working" anyway by subsituting a short, like
a piece of wire again, for the switch.  Now you'll know the ecu is
seeing zero like it should, does this make it idle right?  if not, your
switch is not the problem, if it does, clean or replace switch.

--
Huw Powell

http://www.humanspeakers.com/audi/

http://www.humanthoughts.org/