Date: Mon, 6 Jun 94 10:40:40 CDT
Sender: Vanagon Mailing List <vanagon@vanagon.com>
From: smitht@jupiter.sun.csd.unb.ca (Tim Smith)
Subject: Re: engine surge at 1100rpm
> i am still battling an engine surge 1100-2000 back and forth in my
>'85. it doesnt fit the pattern of the one for which the auxiliary wiring
>
This problem happened to me when my '85 vanagon was still under warranty, VW
couuldn't fix it either. It turned out not to be one component of the FI
ssystem, but three. The idle sensor was out to lunch, the O2 sensor
likewise, and the airbox (throttle flap). The regular repair procedures are
to pull each
component, replace it with a KNOWN good one, then try again. This won't work
if more than one component is causing the problem. VW replaced these and the
main FCU on my van etc. etc. individually, and eventually told me 'all vans
drive like this, get out'. this after a six month period, during which my
van spent 27
days in their shop! The FCU has default settings if you disconnect the O2
sensor, but it can't correct for a deranged one, so pull the lead to
isolate that component, then swap the idle stabilizer for a fresh unit.
DON'T TAMPER with the airbox settings, a small screw hidden under a blue
cap on top of the box. This is a factory calibration unique to the airbox,
not to your car! Make sure the flap moves freely, any backfires can damage
this by driving the flap against the stops. You can verify the electrical
resistance reading on the flap as it moves, they should change smoothly as
it is moved. Check the idle switch, near the throttle body/cable. Bently
manuual is very useful, and $$.
Be prepared to spend some time on this. You need to try components when the
engine is completely cold and then throughout the warmup/ normal region.
Dying electronics are more temperature sensitive than normal (or dead) ones,
and elusive to track down.
My surging deteriorated to no power off idle, I had to rev high, slip the
clutch to get moving. If it started to die even then, it was terminal, coast
to the roadside, turn it off, wait a minute, restart and repeat. Didn't work
well in the big city! Eventually it would die while in motion, 45mph 3rd
gear, a real blast when heading up a freeway on ramp. good luck, tjs
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