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Date:         Tue, 18 May 1999 21:45:13 PDT
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:      Engine Pulsing
Content-type: text/plain; format=flowed;

Volks -

Some of you may recall that I had an interesting trip from Atlanta to Moscow Idaho in March. My '87 Westy had the bucking engine really bad, and a mechanic in Colorado Springs diagnosed a bad ECU. When I headed down the road the next day, I had the same problem in Wyoming. The VW dealership in Casper (nice folks, by the way) installed the wiring harness and re-adjusted the engine. I ran OK from there back to Moscow, although it felt to me as if the engine were pulsing just a bit at times. The engine idles very smoothly at about 900 RPM.

Since then I haven't driven it much. A 90 mile trip to Spokane left me feeling that I still have a minor pulsing problem, and I did notice it while driving at a steady speed in town, both with the engine cold and hot. Last weekend, several of us drove to the Columbia National Wildlife Refuge, near Moses Lake, WA. to go hiking and canoeing. It was a nice weekend, but both coming and going, I could feel that the engine was pulsing just a bit, mostly when I was just rolling along, not accelerating hard. Also, I didn't get very good gas mileage. 18 mpg going over, and 18.5 coming back. I was the only person in the van, and I wasn't heavily loaded or carrying things on top of the van. This isn't anything like the bucking and power loss I felt earlier, but if it is a symptom of another problem, especially one that could strand me by the side of the road, I would like to solve it!

When I got back, I dug out some articles I have been saving, and decided to check out the AFM. I bought a decent multimeter and some electronic spray cleaner, and carefully removed the plastic top. The interior looked clean and unworn, although I could see a pair of thin lines in the black semicircular contact surface where the spring loaded brass piece rubbed along it.

According to Kay Fremgen, Bosch says that if you measure the voltage between pins 2 and 3 while you are moving the air vane, it should smoothly change from .2-.3 volts to 4.5 volts. On mine the rest position was 4.6 volts, and as I rotated the wheel that controlled the air vane, the contact swept smoothly across the black strip and the voltage dropped evenly to .4 volts.

Looked good, although it would have been nice to see some evidence of the problem.

I sprayed it with some Radio Shack electronics cleaner, and while I was waiting for that to dry, I unscrewed the ground wires from under the air conditioner compressor, cleaned the connections, even though they looked pretty good, and tightened it back down. The other end of the strap looked as if it has recently been cleaned, so I just loosened it, worked the wires against each other a bit, and re-tightened it.

Re-checking the AFM returned the same values, so I reassembled everything and went for a test drive. There is still a little bit of stumbling while under mild acceleration, but not full throttle. A ten mile drive revealed almost no pulsing, just a very little bit a couple of times.

I wish I hadn't touched the ground wire, because I don't know which of them had an effect!

Now - the problem is I want to go on vacation next month, and it would be nice if I didn't have to spend the trip worrying about the engine. What should I do to eliminate the pulsing completley? Steve recommended doing everything I have done plus replacing the coolant temp sensor, 02 sensor and the fuel filter. Shoule I just spend the money as preventive maintenance? I have no idea how old any of them are, because I just got the van.

The voltage check indicates that, at rest, the AFM is working properly, but is it likely that there is a problem when it's running? Is this likely to become a more serious headache?

Thanks for any suggestions, and for putting up with my logorhea!

Mike Finkbiner

'87 Westy

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