Audi 100 (5000 in US?), 5-cyl 10v engine troubles... Help!

[quk@sievers.com (Phil Payne)]

In message <199703081714.RAA27671@richmond.premier.co.uk> Mike Walder writes:

> I started noticing a lack of power at the higher revs,  resulting in a lower
> top speed.  This has now degraded to a state where I can only achieve 75Mph
> in top gear, 65 up hill.  This is no great problem, as the speed limit here
> is 70Mph.

Check warm-up regulator and full-throttle enrichment, in that order.  The warm-
up regulator check requires a Bosch or compatible "continuous injection" 
pressure gauge, but a competent garage should be able to do it in 1/2 hour.  
The full throttle enrichment issue is a bit more complicated - see if you can 
get the appropriate Haynes manual from your local library.

> The main problem seems to be associated with cylinder 4, as the plug fitted
> here is black (i am unsure whether this is carbon or oil), as the others are
> golden in colour.

Inconclusive without a compression test.  A simple compression gauge costs very 
little - screw out all the plugs, earth the high-tension output from the coil, 
screw the gauge into each cylinder in turn, and spin the engine on the starter 
with the throttle open.  Let us know the readings.
 
> Also, when the engine is revved to 5000+ rpm, a cloud of grey smoke comes
> from the tail pipe.  I was told that this was because of over fuelling, but
> others say it may be head problems.

Grey smoke, if truly grey, is indeed quite likely to be a head (or head 
gasket) problem. Does it smell of vapourised oil, of burnt oil, or more "acrid"?

> Any suggestions would be greatly appreciated,  I'd like to keep it on the
> road, as it is in excelent condition for a 15year old car.

Why not?

--
 Phil Payne
 phil@sievers.com
 Committee Member, UK Audi [ur-]quattro Owners Club