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Date:         Wed, 20 Mar 2002 04:09:12 +0000
Reply-To:     Mike Finkbiner <mike_l_f@HOTMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Mike Finkbiner <mike_l_f@HOTMAIL.COM>
Subject:      Cough, Choke, Splutter!
Content-Type: text/plain; format=flowed

I am having an interesting problem with my '87 Westy. I drove about 300 miles to Seattle, getting about 14 mpg, significantly worse than I normally get. When I got off the freeway and started trying to find a parking place, the van started running rough, loosing power, and trying to die. I parked, and went into the bookstore I had come to, figuring I would let it cool down and see how it was running then.

After an hour I came out, started it up, and it ran OK. A few minutes later, though, it started acting worse than before, no power, wouldn't accelerate, engine pulsing, backfired. I managed to pull off the street, and checked my digitool.

The O2 sensor, which should have been running around .5 volts, was, IIRC, over 9 volts (!), so I moved the stuff out of the back, unplugged the O2 sensor, fired it up, and things ran fine. I figured I must have a bad sensor, or a wiring problem, and hoped I could run it in open loop until I got home. The digitool reading was now .35, which seems a bit low for the default setting. I thought it should be about .5.

Things went OK for the next 100 miles. Gas mileage was better, and the van ran OK. Then, in a pouring rain in slow moving traffic, it started losing power, and trying to die. I re-started, and things went OK.

The next 180 miles was some city but mostly freeway. The van ran fine, but only got 13.5 mpg when I filled up in Seattle. I headed east over Snoqualmie, and it seemed to have reasonable power, but still only 14.6 mpg when I filled up in Royal City.

I stopped for dinner in Othello about dark. When I got out and headed out of town, it was just like the time in Seattle, engine pulsed, wouldn't accelerate, kept wanting to die. Backfired a couple of times. The engine wouldn't keep running unless I kept my foot into it. While stopped at a light, I did see a cloud of dark smoke come from the back of the van. Each time I re-stared, it would run OK for a short time. I poked and prodded, couldn't find any obvious problems, so spent the night there.

Next morning I got the multitester and looked for ground problems - didn't find any. No obvious disconnected wires, except the O2 sensor, and no loose vacuum lines. When I warmed it up, things ran fine. Couldn't make it act up. So I headed home, and in that stretch got 13.8 mpg (Ugh!).

After I unloaded, I reconnected the O2 sensor, to see if that would cause it to malfunction. No problem. The digitool readings were bouncing up and down around .5. The van ran fine around town. Ran fine this morning going to work.

Coming home for lunch, the digitool readings for the O2 sensor were negative, -.1 / -.2 or so, until it warmed up a bit. When I got home, idling in the driveway the readings were negative again, -.15. After lunch, I had a milder episode of the same problem. No backfiring, but no power, wouldn't accelerate. I pulled over, disconnected the O2 sensor, and it ran fine.

The throttle position switch indicator light comes on when it should. The AFM seems to give the same sort of readings it usually does, no jerking, but I haven't had it on that setting when I have had problems.

Seems to me that there are several potential sources of the problem -

1) I did not dance widershins around the van before leaving on the trip 2) The wiring to the O2 sensor has an intermittant short or ground 3) The ECU is going bad 4) The digitool wiring is causing a problem 5) Something else

The ECU is a two year old Bosch. The Temp II sensor was new last summer. I have the wiring harness on the AFM, and have cleaned the wiper path. The O2 sensor is a Bus Depot generic, about two years old. The one it replaced was also soldered, and the wiring that connects it to the wiring harness near the coil looks worn.

The fact that it re-starts easily, and run OK for a brief time afterwards indicates that it's some sort of sensor problem, or a problem with the way the ECU is dealing with signals. Re-setting it by turning it off will solve the problem until it settles down.

I hate intermittant problems like this, and am not sure how to figure it out. At first I hope replacing the O2 sensor would do it, but after it acted up while in open loop, it doesn't look like it.

The 9 volt reading I think I saw in Seattle worries me. If it had a partial short through the wires, could that have damaged something?

Any suggestions for things that could be causing these symptoms? I thought if the O2 sensor was grounded or shorted, the ECU would just go to open loop?

Thanks for any suggestions!

Mike Finkbiner '87 Westy Moscow, ID

Mike Finkbiner mike_l_f@hotmail.com

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