IAC

[thomas walter x5955]

Dan,

On the IAC, I found the unit fitted in the BMW to fail in the OPEN
mode. It allowed too much air to enter the engine (at idle the engine
would rev to over 1200 rpm... the ECU sensing the engine would cut
the fuel - dropping the rpm back, which the ECU would respond with
a fuel flow again... ).  Quick fix was a penny with a 1/8" hole
drilled in it. This would limit amount of air the unit could pass,
preventing the engine from doing its VROOM, VROOM trick.

Long term fix was to repair the VDO box. The FET on the output
stage was not fitted with a heat sink. With excessive heat and
age the solder joint would fail. 

[Oh, I slipped off the hose to the IAC, fitted the -ahem copper
slug- with a hole in it next to the IAC metal flange, and slipped
the hose back in place]. 

Cheers,

Tom Walter
Austin, TX.