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Date:         Tue, 12 Oct 1999 14:49:44 -0400
Reply-To:     "Karl F. Bloss" <bloss@ENTER.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         "Karl F. Bloss" <bloss@ENTER.NET>
Subject:      Digifant throttle position switch
Content-type: text/plain; charset=US-ASCII

This messages comes from Damian Shaw, who posted it to rec.autos.makers.vw.watercooled. I contacted him to make sure it was OK for me to repost it here and he agreed.

If you have questions, please e-mail him: Damian Shaw <damian@billgood.net>

-Karl

-----------------

Thought I'd post this to hopefully help others aviod the headaches this gave me.

The problem:

My Vanagon (87 Dignifant FI) liked to rythmically 'idle dip' when warm (800 rpms -> 400 rpms -> 800 rpms . . . ) drove me nuts! Sometimes when cold it would stall out when pulling away from the 1st stop sign (usually my second stop).

After some diagnostics it was pretty obvious that the throttle position switch was to blame. So I set out to adjust it to spec (as per Bentley).

Problem was it was VERY hard to get to spec. Over the period of 6 months or so I must have adjusted it 5 or 6 times. Even when doing the adjustments it would be correct until I cranked down the fastening bolt. It was VERY frustrating.

Eventually I pulled the whole throttle off the van and checked the switch. Switch worked fine. (DON'T let people talk you into changing this until you've check it off the van - I had many people (and I appreciate the help) suggest this. It's easy to think that will solve things - it doesn't unless you know for sure the switch is bad. Check it by taking it off the throttle body and using a multi-meter.

I adjusted it off the van, put it back - soon enough: No good. (It SEEMED to be a lot easier to adjust off the van - more on this in a sec.)

Next moved - Pulled the throttle body off the van again and replaced the little plastic cam that activates the switch. Put it all back together and on the van. Shortly afterwards: No good.

Off comes the throttle for the third time. This time I notice that the spindle the butterfly turns on has just the slightest bit of play in it - and right at the closed position too! Now bear in mind - this play was TINY. But - with the switch tollerances so small - it was enough to screw the switch up. This play essentially put the idle switch in a state chaos - sometimes it would activate at idle - sometimes it wouldn't. But it was SO SUBTLE!

THE FIX:

I took the spindle out of the throttle body (you have to remove the butterfly with a Torx screw driver - but you DON'T have to remove the top bolt (that holds the spring down) on the spindle - just move the springs around - the spindle pulls right out. It is important to know this - I thought it was a scary thing to attempt - but it came apart very easily. VERY IMPORTANT NOTE: DO NOT change the postion of the idle rest screw (painted red) - that's a factory adjustment only and will cause you to hate life! I cleaned it all up. Also removed the grease seals at the top and bottom - cleaned them. Re-greased it. (The spindle, BTW, definately had worn spots on it) Then I wrapped the worn areas of the spindle with teflon tape (the kind used for plumbing connections) and put it all back together - took a couple tries to get the tape in place - the grease REALLY helps. PRESTO! - Nice and tight spindle - no binding - nice and fluid motion. I then adjusted the switch - put the throttle back in the van - AND adjusted the switches again

(NOTE: the tollerance is so tight on this you really can't adjust it outside of the van and assume it's right - I made this mistake on a prevous adjusting session. The trouble is when the tensor spring is added and worked thru its range (WOT to Idle) everything is in a little different place - Remember this and it will save you a headache or two...)

Ran the van.

Adjusted the idle.

He's happy again!

Another note - although I used a multi-meter on the switch to determine if it was working, you can, as a quick test (and only as that), just LISTEN for the switch to activate at idle and then again at WOT (it will always activate at WOT regardless of adjustment). If you can hear it activate at idle you're on the right track - no activation at idle is worse than a gap that is too large.

I hope this helps someone someday - this little issue ran me in circles for months. It's not a life and death thing - but, for a nut like me, it was VERY annoying.

Feel free to email me with questions.

Damian '87 Westy; '89 Cabriolet


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