Failed emissions due to timing? Can it be?

Dan Cordon cord4530 at
Thu Apr 8 01:29:48 EDT 2004

> Subject vehicle is a 1989 200 turbo quattro sedan,
> early MC engine with single knock sensor.
> The youngster at the smog station claimed "the timing
> measures 10 degrees BTDC and it should be 15 degrees".
>  The Bentley confirms it should be 15 degrees, however
> it also claims it's not adjustable.


I haven't experienced this first hand, but isn't it pretty common for 
the front pulley to slip out of alignment? I thought I've heard many 
people doing TB jobs and found the TDC reference had moved notably. It 
could be that yours has slipped 5°. Just a thought anyway.

While improper timing can certainly give poorer emissions, you didn't 
mention if your car passed (or was tested yet). Could be your timing is 
fine with the pulley slipped, or it could be the ignition is being 
retarted by the ECU too. Perhaps it's falsely detecting knock?

Dan Cordon
Mechanical Engineer - Engine Research Facility
University of Idaho

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