Date:         Mon, 17 Jul 2000 09:58:09 -0400
Reply-To:     Gary Stearns <gstearns@sprintmail.com>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Gary Stearns <gstearns@sprintmail.com>
Subject:      Our beloved digifant
Content-Type: multipart/alternative;

I'd like to take advantage of the collective wisdom of The List.  I need some basics on the operation of the digifant system.  I too have had problems with the lumpy idle, stalling etc.  I have replaced everything except the AFM (which checks OK with a cheap digi multi-meter) and the computer. I have messed repeatedly with the  "don't even think about touching this" , mixture screw.  I finally decided to experiment on the AFM with the adjustments that are found on the "wiper" under the small plastic cover.  Tried changing spring tension.  Looser (allowing wiper to move more for a given volume of air) helped some.  Changing the position of the wiper contact relative to the air flow vane (richer) helped alot, **but** only with the 02 sensor disconnected.  When I reconnect the 02 sensor, everything returns to crap.  The easy answer is that I need to replace the 02 sensor right?  Did that 2 years ago.  Ran like crap before and after the new sensor.  While doing my experimentation, I have connected the multimeter to the 02 sensor output (while sensor is disconnected from the computer). It is working.  All of the basics are correct: no vacuum leaks, good ignition, new fuel filter, idle stabilizer, etc.  The static timing is advanced @ 5 deg.  Makes more power this way, and does not seem to effect anything negatively.    The engine really only wants to run well when the 02 sensor shows that it's running very rich: .80 to .90 mv.  At this setting, it really does run well.  Steady idle, no stumble on clutch release, no popping and kicking on decel, and gobs of power at cruising speed.  The question then is: why can I only get this thing to run right when the injection is apparently too rich?  Is this what VW intended?  Is this the only way that it would pass emissions specs or get acceptable mileage?   Does the 02 sensor provide input to the computer at all operating speeds/loads or just at idle?  Does the C0 adjustment screw affect the entire "map" of operation or just at specific speed/load or when the 02 sensor is out of the loop?  I am very happy with the way our wbx is running now, but this setup is not right.  Why?

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