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Re: 4kQ, running rich

When my 911 did this, it was weak spark and required a new ignition system.
I took that opportunity to install an MSD at about 1/2 the price of a new
The car would turn  brand new plugs black in about 3 miles of driving.

mike miller
91 200q

-----Original Message-----
From: Orin Eman <orin@wolfenet.com>
To: Quattro List <quattro@coimbra.ans.net>
Cc: Pete Kunzler <pck@gte.net>
Date: Tuesday, June 09, 1998 12:50 AM
Subject: 4kQ, running rich

>Pete's 'old' 4kQ is running really rich.  Any ideas?  We have checked
>the following:
>Plugs are uniformly fouled - black.  New plugs didn't help.
>Compression 140 to 170.
>O2 sensor heater resistance OK.
>Differential pressure regulator OK.
>Temperature sensor OK (swapping for known good and vice-versa).
>O2 sensor reporting rich.
>ECU is pulling differential pressure regulator current
>down to 0mA.
>After a full turn of the mixture screw it is still rich
>and running poorly, though the O2 voltage came down slightly.
>(This is way too much to turn that screw in normal circumstances.)
>System fuel pressure is 5.8 bar, differential pressure 5.4 bar
>which is close enough given the JCW guage.
>Cold start valve is neither squirting nor leaking.
>The fuel pressure remains over 40 psi after shutdown.
>The air flow plate is binding very slightly (hard to feel,
>but there neverthelesss).
>This was a sudden failure, not gradual.
>It seems to me that the ECU and electronics are working
>and that the problem must be mechanical - either the fuel
>distributor or differential pressure regulator.
>Any other ideas?
>Please reply to 'all' to include Pete as well as myself/the list.