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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