Date: Thu, 5 Oct 2000 12:36:28 -0400
Reply-To: "David Hagen (by way of Derek Drew <derekdrew@rcn.com>)"
<sportscar@MINDSPRING.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: "David Hagen (by way of Derek Drew <derekdrew@rcn.com>)"
<sportscar@MINDSPRING.COM>
Subject: Euro-Drive: FIX 89 Volkswagen vanagon, Emissions/Poor-idle
Content-Type: text/plain; charset="us-ascii"; format=flowed
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1989 Volkswagen vanagon 2.1 L
Trans: Standard
Mileage: 100,000 mi
VIN: WV2YBO25XKHO64820
Fuel: digifont
Ignition: hall
Symptoms: Excessive Emissions, Poor Idle Quality, Hesitation, Surge,
Cuts out, Stall, Misfire, Poor Fuel Economy
Occurs: Always
___________________________ FIX: ___________________________
Good news, 1)ECM sent out and repaired, still has sawtooth
pattern on ground. Is this normal ? Any VW waveform Guys ?
3)Replaced 2 apparently defective Bosch 02 sensors with
NGK. (works correctly) 4)Replaced Alt with bad diode
5)Cleaned and/repaired all grounds. 6)Checked integrity of
wiring harness 7)Replaced coolant temp sensor. The vehicle
now runs well, good power,throttle response, 02 waveform
and function, stable idle, no richness noted. The key
seemed to be the ecm repair, and no more funny O2 sensors.
According to the repair tech, many solder joints had
faults. Does anyone have any knowledge on digifont ground
waveforms, what they should look like, and shouldn't and so
forth. We would really like to know. Thank You
____________________ ORIGINAL MESSAGE: _____________________
Dear VW drivability people, Has anyone seen this before ?
Sawtooth current ramp on sensor grounds and B at ecm. No
ground control at O2, tps and airflow meter. Customer says
'I noticed my alt light coming on so I put in new brushes'
After the initial diagnose. Find leaky diode at 4000 rpm.
Hmmm, could this ac voltage have found it's way back to the
main power transistors in the ecm? Also if the brain is now
schizophrenic can it be negatively biasing the O2? On cold
start, good run (open loop) into closed loop , rich rich
rich. O2 then begins to run backwards. Try new O2, runs
excellent for a few miles. O2 waveforms look good then
everything dives ! O2 now is biased negative. When looking
at sensor ground waveforms and B Alternator waveform, a
long sawtooth pattern is present, interestingly enough,
when the alt is taken out of the system, the long sawtooth
disappears but it is superimposed over a current ramp of .5
volt that toggles 3 times then disappears for a few seconds
and returns again.(bad trans on ecm ground switching ? If I
had not looked at this without the alternator disconnected,
I never would have seen the other waveform. The alt has
been replaced. All grounds have been cleaned and checked.
Original complaint, no power. Found cat torched and
blocking muffler. did ac kill this ecm,o2,then cat? Bad
ground and B waveform looks like bad transistor shutting on
and off. Fred, SportsCar Eng.
David Hagen
sportscar@mindspring.com
Owner/Technician
SportsCar Engineering Ltd.
Moorhead, Minnesota, USA
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