Weird MC engine problem

[Bernard Littau]

Hi Phil,

[lots of snips]
> > Interesting.  Did you power wash the engine?  You may want to check the
> > distributor, especially the cap.  I've seen water or other
> foreign material
> > in the cap.  I've had these cars idle fine, but buck and stall
> under load or
> > increased rpms.  Foreign material can cause all sorts of
> crossfire events,
> > which might explain the backwards running, and the stall.
>
> Nope.  No wash and the distributor has been out and cleaned so
> many times ...

Well, this is belaboring the point, but I've had water mixed in with the oil
turn to vapor, and settle in the distributor cap once the car gets warm.  I
don't believe this would occur on an MC due to the crankcase being purged
into the intake.

>
> The only oddity - at some time someone has scratched a 'new'
> alignment mark in the top of the
> distributor body wall.  It's about 5 degrees advanced from Audi's mark.

Scratches on the outside are OK, scratches on the inside are a problem, and
can cause crossfires.  I'd consider swapping the distributor, plugs and
wires, for known good.

>
> > You're not off by one on the plugs, by chance?  Maybe swapped
> two leads?  I
> > suppose it might idle in such a state, though I have not tried this.
>
> Firing order is correct.
>
> I should mention that the car is at a turbo specialist -
> Turbotronic in Woodville.  It has
> every diagnostic device known to man hooked up to it.

Even one of those multi-lead diagnostic analyzers that show all cylinder's
traces at once on a big display.  I've seen these, I think Sun makes the
ones I've seen around here.  One of those would sure rule out any ignition
related events.

Spark, fuel, air; you know this.  If it's not spark or fuel, what does the
turbo look like?  Is it perhaps jamming at higher rpms, when the EGT or flow
goes up?  Then it un-jams after it cools for a few minutes?

It revs cleanly with no load, and stalls suddenly under load, and will not
immediately restart, and bucks when it will not start.  No codes.

Nice little Friday afternoon stumper for us non-specialist amateurs :-)  Do
report when you figure it out.

Best,

Bernard Littau
Woodinville, WA