Idle Questions

["Jeff Wolf" <jeffwolf@cdc.net>]

I have a couple of questions regarding some poor idleing.

A few weeks ago I wrote to you all about my buddies '88 5000cstq that would
only idle high.  As per your suggestions we checked the Throttle position
switch and it seems to be fine.  We also cleaned the ISV and that seemed to
fix the problem but only very temporarily.  After 4 or 5 revs, the engine
idles from 2200 to 2800 RPM.  

My questions are:

1) Can this high an idle be caused by a bad ISV or does this indicate other
problems.

2) Could the Idle adjustment screw by set way off or is it more likely to
be a vaccuum leak in one of the many hoses.

3) If you run the engine with the ISV disconnected (Will doing this for a
minute or two damage the engine?) what should the idle speed be?

4) What is the best way to check for leaks in vacuum hoses, and which ones
are most likely to be bad and/or causing these problems.

5) How do you dump the engine fault codes?


Now for some help with my car :)  I own an '89 100 (no turbo or quattro). 
The car runs and idles fine except when idleing with the air conditioning
compressor on.  when this happens the idle drop to about 550-600 rpm
resulting in a very rough running engine.  Could this problem be caused by
the Main idle adjustment (is there such a thing on my car?) being set too
low so that even with the ISV compensation the idle is still too low?  Can
I just disconnect the ISV and see where it normally idles?


Thanks for all your help,


Jeff Wolf