Date:         Tue, 5 Sep 2000 17:22:12 -0400
Reply-To:     Wolfgang Ziegler <ziegler@PRINCETON.WIRELINE.SLB.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Wolfgang Ziegler <ziegler@PRINCETON.WIRELINE.SLB.COM>
Subject:      Emission / Air Mass Sensor - could it be the cause?
Content-Type: text/plain; charset="us-ascii"

Hi,
I am new to the list - thanks for helping me out. I searched the archives and found some valuable hints.
Have been facing an increasing problem with my 88 Vanagon (106 kmiles) over several months now:
Symptoms:
Very little power, sluggish when below 2000 rpm, especially in warm climate and/or with AC on
Very high idle emissions (HC close to 1000 - CO 1%), prev. years <100
No performance problems with O2 sensor disconnected (HC close to 1000)

Steps taken:
clean and reseat all connections: ECU, sensors, Idle control...
new sparks, wires, distributor, air filter - timing tuneup
new temp sensor, O2 sensor
check for vacuum leaks, check idle control valve

Suspects:
The resistive layer of the air mass sensor shows wear by the wiper. The 'over-all' impedance is about 300 Ohms (as defined by the individual resistors), when measured on the wiper (analog meter) I see the values between 25 (closed) and 300 (open) vary all over the place - not monotonously increasing. Is this because of the high impedance of the black conductor or is the unit faulty? What should the reading be for the idle position (1/3 open)?

Will a new unit require major adjustment - have not seen anything on a how-to

What is the correct procedure to adjust timing for the Digifant system? - engine warm up - disconnect temp sensor - adjust at 900 rpm?

I appreciate your help - need to get through inspection soon.

Wolfgang Ziegler