Re: smog test from hell

[Aleksander Mierzwa <alexaudi@kki.net.pl>]

At 02:48 99-10-11, William P. Magliocco wrote:

>Last week I took my '86 5kT (MC engine) to have a smog test done at the
>local garage.  
>
>The first time on the dyno it failed.  The mechanic attempted to get the
>car to pass by tweaking the timing, then playing with the CO mixture
>adjustment on the air flow plate in the CIS box.  Neither allowed the car
>to pass.
[...]
>All well and good, but now the car has become a dog to drive.  At idle and
>to about 1500-2000 RPM one can feel the car missing on a cylinder and also
>some shudder due to the miss.  In the 2000-3500 RPM range it seems ok.  I
>just drove the car from Phila. to DC over the weekend and it wasn't too bad
>on the interstate.

Never, ever allow a smog test station mechanic to fiddle with the engine
management settings on an Audi. 
- You can't adjust timing on these cars unless your last name is Mockry or
Ritchie so you know how to reprogram the chip inside the ECU. Timing is
non-adjustable on these cars and the only thing you can eventually do is
cause a no-start condition (BTDT at a local moron VW/Audi service).
- As long as your oxygen sensor is connected and working you can't adjust
emissions level at idle and part throttle by turning the mixture adjusting
screw. The ECU will always try to compensate by altering the frequency
valve duty cycle until it hits 0 or 100% duty cycle, but then someting is
seriously wrong with your engine. You can, however, cause problems with
cold starting at WOT running.
I would start with checking the timing (as long as the car starts and does
not report any error codes it's probably OK, though) and mixture setting (I
bet it's way off right now).

--
Aleksander Mierzwa
Warsaw, Poland
87 5KT