Date:         Sat, 13 May 2000 19:35:07 -0400
Reply-To:     Dave C <happycampers@PICUSNET.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Dave C <happycampers@PICUSNET.COM>
Subject:      Re: Hesitation with acceleration
Comments: To: Tom Moritz <tmoritz@BMI.NET>
In-Reply-To:  <3.0.3.32.20000513132211.00708030@mail.bmi.net>
Content-type: text/plain; charset="ISO-8859-1"

on 5/13/2000 1:22 PM, Tom Moritz at tmoritz@BMI.NET wrote:

> I would appreciate some assistance in diagnosing a problem we are having
> with our 90 Westy.  We recently had the engine rebuilt due to a broken
> cylinder head stud.  Then engine runs great except for a hesitation when
> accelerating.  The problem is most evident when pulling away from a stop
> light or stop sign.  I sometimes feel it when I'm accelerating in traffic.
> 
> Here's a decription of my perception of the problem.  I'm stopped at a stop
> light and it turns green.  I'm a gentle driver so I depress the accelerator
> peddle 1/8-1/4 full travel.  The car just rolls forward as though I've
> released the brakes but not given any gas.  Then 1-1.5 seconds later the
> car will start to respond to the accelerator input.  Full accelerator input
> results in normal rapid vehicle acceleration for that pedal position.
> 
> I have the following suspicions and would appreciate any feed back on these
> or other possible causes:
> 
> 1) My airflow meter is failing and the vechicle is accelerating when the O2
> sensor corrects the mixture.
 It is possible to move the carbon swipe track just a little to give new
surface to read from. Remove the top of the AFM, loosen the screws that hold
it down a bit and push the bugger over a tiny hair.

> 2) The bypass on the airflow meter is not set correctly.
If you're refering to the 5mm allen screw in the AFM, then yes, it sets the
CO levels. One can use the O2 sensor to set the CO level to correct this.
Someone else will have to give specifics of actually doing this.

> 3) I have a bad temp sensor (though this problem appears to be independent
> of operating temperature.
 If you're refering to the Temp II sensor, yes thay can go whacky and still
read in tolerance. I had one do this once. They don't cost that much and are
easy to put in.

> 4) Others?
Make sure your timing is right. Sounds like it could be a little retarded.
Vinnie actually likes to be at 6º instead of the factory 5º.

Make sure your throttle switches are clean and set correctly.
In short, go around the engine (with your Bentley) and confirm that the
settings of the various sensors are within spec. After they are, make small
changes, test, go from there.
Hope this helps,
Dave C.
Williamsburg, VA
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'85 GL Westy (His)
'91 Cabriolet (Hers)