16V Hard Start

["Christian Els" <tiAn@usiw.net>]

My car has become increasingly hard to start when it warms up. It starts OK
from dead cold, but as the car and the ambient temperature increase it
becomes unnervingly hard to start reliably. This afternoon I had to
disconnect the O2 sensor before it finally caught. That points to a mixture
issue, in my mind. Yes?

Driveability once started is good, maybe just a little weak on the bottom
end.

I just finished nailing down the mixture (thanks, Bill Scarince), ignition
timing, the air flow plate height, and the O2 sensor is only ~500 miles old
(and returns correct values).

I am unable to clarify to myself what role the knock sensor might play in
this problem after reading Bentley. I would think that if it is bad, that
would not manifest itself as a starting problem, but rather general
driveability, correct?

I am starting to wonder if the ECU is faulty rather than adjustment issues
elsewhere in the system. Does this seem a reasonable conclusion, or I am
jumping to that too hastily? I have not yet verified fuel pressure, but both
pumps are ~500 miles old, and after starting the car does drive just fine.

TIA,

Christian Els
87 Scirocco 16V
stuff...



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