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1988 Volkswagen Vanagon

Engine:        2.1 L / 4 cyl / Gas / OHV
Fuel:          Fuel Injection / Bosch AFC EFI
Ignition:      Distributor-Breakerless / Hall Effect Distributor
Trans:         3-speed Automatic Transaxle
Mileage:       140,000 mi
Emissions:     Federal
VIN:           WV2YB025XJH

Symptoms:      Excessive Emissions, Poor Idle Quality
Occurs:        Hot, Idle

_______________________ CLOSED W/FIX _______________________

Hello Again:

MOD is wrong again. Pin 20 on the ECM should be grounded.
We believe that it has something to do with the O2 sensor
service reminder light. Once we grounded the gray/white
wire the system went into closed loop and the CO% reading
came crushing down. It even passed the Ontario Drive Clean
ASM test beautifully.

Several replies confirmed that these engines idle on the
wobbly side and pulse width of 3 msec+ at idle is quite
normal.

Thanks so much to all those who responded.

Eli

_____________________ ORIGINAL MESSAGE _____________________

Hello VW Experts:

We've got an 88 Vanagon that's proving to be a pain. It was
sent to us from another shop after spending considerable
time on this beauty.

The complaint is that after a few minutes following a cold
start, it starts to run rich, spewing black smoke along
with a shaky idle. This seems to be a basic Bosch AFC port
injection system. We followed the diagnostic charts,
checking all powers/grounds/sensors etc right at the ECM.
Everything is within spec. Fuel pressure is a steady 30 PSI
at idle. The O2 sensor has been replaced and is pegged at 1
volt. The enrichment/idle switches are functioning. The
coolant sensor has been replaced and another ECM was
apparently tried without success. There are no vacuum leaks
and ignition timing is right on. On a cylinder balance
test, all cylinders seem to do something. The only sensor
in doubt is the air-flow. Playing with the CO adjusting
screw makes a difference (all the way to a stall) but not
improve the rich condition. One strange item: The flap of
the airflow meter vibrates at idle (intake pulsations?) The
injector pulse-width at idle is about 4 msec. which seems
high. The injectors hold pressure with the engine off.

Any ideas will be appreciated

Eli

Eli Melnick
melnick@home.com
Owner/Manager
Start Auto Electric Ltd.
Toronto, Ontario, Canada

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