Re: Funky Idle - '87 5kTQ

[rademer@rbg.informatik.th-darmstadt.de]

Mike described his problem with dropping idle -- down to 500rpm etc.
I have fiddled with this problem longer than a year now. I acually HAD
connected LEDs to the idle-stabilizer-valve, to the idle-cutoff-valve (sp?)
and to the cold-start-valve to monitor the motor. Doing this I discovered
a faulty idle-control-module not powering the cut-off-valve. 'Cause a new
module is too expensive I opened it and tried to bugfix. The reason was
a shot transistor (50 cents...). But I could not found anything for
the idle... 

Till now i cured the problem a little with adjusting the idle-screw
and cleaning the valve. But its not working 100%.

Yes its true. The valve will shut off if disconnected and connected back
it will stay closed until shutting the car off. The same symptom you get,
if you pull the connection to the thermo-resistor (in my car at the front,
brown cable) and put it back. The control-module sends impulses to the
valve, so the LED in my dash is not as bright as with 12V normally.
Although i cannot monitor the valve working, the brightness of the LED
does change to few. The module will only start to power the valve, if the
connected resistance is abut 20 Ohms. If you have lower or higher impedance,
it will not work.

BTW. Does someone know the answers to the following questions (refering to
a Audi 100'87 motor "KP", no AC, K-jetronic, *with unregulated cat*?

 - What is the vacuum-line going to the idle-cutoff-valve for?
 - Where can I get a circuit diagramm for the idle-control-module?
 - What are the connections "K" and/or "KA" on the module are for?
   (my book says something about a AC-Compressor, and if I connect 12V
   to one of them the idle raises about 20rpm..., normaly the are open)

So long and happy Audiing...!
Ero.