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Date:         Tue, 6 Mar 2001 09:13:09 -0500
Reply-To:     Gary Stearns <gstearns@OPTONLINE.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Gary Stearns <gstearns@OPTONLINE.NET>
Subject:      Re: More O2 Sensor confusion...
Content-type: text/plain; charset=iso-8859-1

As anti social as it is...I've been running with the O2 sensor disconnected for about 9 months. The sensor is now connected to a voltmeter on the dashboard so that I can see what's going on. For 3 years I have tried everything to get our van to idle correctly and run correctly. The idle always sounded like there was either a major vacuum leak or we were running a full race cam that wasn't supposed to idle correctly. With 3 different O2 sensors the result was always the same. 18 months ago we installed a rebuilt short block and transferred all of the intake/injection equipment from one engine to another. I looked for problems, and very carefully reassembled everything. New injectors, new fuel lines/filter, new fuel pressure regulator, etc. After the shakedown cruise, the new engine stumbled just like the old one! I discovered over time that the basic settings on the vane in the AFM were way off. Far too lean at idle, and a little too lean at cruise throttle. When I manually set the AFM to run near .50v in open-loop, the stumbling is just like when in closed-loop. I fiddled with the AFM for months and finally got it so that it has a rock-steady idle and makes good power. The voltmeter shows O2 sensor outputs varying between .75 and .82 (I seek power and smooth running). The off idle torque is far better than it's ever been. My mileage is as good(19 mpg), and there is no evidence of the cat overheating or plugging. If I reconnect the O2 sensor to the ECU, it all goes south again, O2 voltages drop way below the .50 that the cat wants to see, and the idle goes back to it's old stumbling self. I've reached the conclusion that VW spec'd the wbx digifant system to run right on the margin of what's acceptable to squeeze the most out of either mileage or emissions.

Gary

----- Original Message ----- From: "Schmidt" <schmidt5@HSONLINE.NET> To: <vanagon@GERRY.VANAGON.COM> Sent: Tuesday, March 06, 2001 6:52 AM Subject: Re: More O2 Sensor confusion...

> Chad, all- I'd like to know the solution to this as I have the same problem. > I recall my 84 having full power and smooth idle while my (1yr) old o2 > sensor was disconnected and I awaited the new one from BD. Symptoms > returned with the new properly installed o2 sensor. I'm sure my mpg would > improve if I dc'd the sensor forever. I got dem ole > intermit-no-power-crappy-idle-fill-the-tank-every-140-miles blues, mama. > Things that MAY affect the o2 sensor performance on mine: I have no cat- > just the straight pipe(cats are expensive). Maybe it is a bad ECU, but why > is it not bad with the o2 sensor dc'd? > I have the feeling that the most affordable, least time consuming answer is > to cut and tape that one little wire. I hate to throw in the towel like > that, but nobody seems to have the answer. > Let me know if you correct the problem. I *KNEW* mine wasn't the only van > with this problem! > Jay > 84 wolfsburg westy > new plugs, plugwires, idle stabilizer, cap, rotor, ignition switch, AFM > cleaned per archives, grounds double-checked, new o2 sensor on 1 y.o. entire > exhaust, no vac leaks, no fuel starvation, no cat to clog yadda yadda yadda > PS: I bet when your symptoms appear, if you shut off the eng for a few > seconds you will temporarily cure this. ARGH! > > > >I originally asked the question about the O2 sensors today and how my > crappy > >idle and hesitation disappeared when I disconnected my O2 sensor. Well > >today I took it upon myself to replace the O2 sensor and low and > >behold......the new one makes it run WORSE. The idle stumbles really bad. > >When I coast to a stop with the clutch pressed in the van almost stalls (ie > >all the leds come on on the dash) but keep running really rough. I noticed > >while coasting to a stop the tach drops really fast all the way down to > >~400RPM and settles around 750-800RPM with the sensor connected. When > >coasting to a stop with the O2 sensor disconnected the tach drops slower > and > >settles smoothly at 1000RPM. Any suggestions what I should do now???????? > >Will my fuel mileage go to hell if I drive with no sensor????? > >thanks, > >Chad 85GL > > >


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