I did some searching through the archives last night on this subject. There
was some guy who says he's done this, but he didn't elaborate much, so who
knows if he's just blowing smoke. Anyway, it looks like that knock sensor is
the only major difference between the Vanagon and Jetta systems. If you
could somehow trick the jetta computer, using the correct resistance of a
knock sensor that is not sensing any knocks, maybe it would work. There are
some other technical differences as well, so I'm sure it's not that simple.
I did confirm from someone else that the Vanagon ECU's are all the same from
I think 83 on, so you could replace the ECU in your 91 Vanagon with one from
an 86 Vanagon. They're all the same part#, but with different revisions (the
letter at the end) I guess VW just made a "better" version every year. If
anyone else has info on this please share. I'm really curious.

>From: "Tom Miller" <tmiller@vcmails.com>
>Reply-To: "Tom Miller" <tmiller@vcmails.com>
>To: "Mark Seifert" <theburnvictims@HOTMAIL.COM>
>Subject: Re:      Re: Actual Vanagon content!!
>Date: Mon, 26 Apr 2004 13:14:53 -0400
>
>I forgot about the knock sensor ingnition on the Jetta.  I guess if you
>swap
>the computer you might as well swap in the Jetta 1.8L engine as well!
>TEM
>----- Original Message -----
>From: "Mark Seifert" <theburnvictims@HOTMAIL.COM>
>To: <vanagon@GERRY.VANAGON.COM>
>Sent: Sunday, April 25, 2004 11:42 PM
>Subject: Re: Actual Vanagon content!!
>
>
> > That's a good idea, because the junkyards have plenty of Jettas, and an
>ECU
> > goes for about 30 bucks. I've thought about this before, but I'm still
>too
> > skeptical to actually try it. It looks like the connector that plugs
>into
> > the ECU is the same, but some of the pins are different. That's why I
>dont
> > think it would work, because although SOME of the controls and sensors
>are
> > the same, they may not go through the same pins on the connector. And,
>some
> > of the sensors may have different resistances, which could send false
> > signals, or some may not even be there at all.  For example, I think the
> > jetta has 2 coolant temp sensors. The Jetta ECU would look for that
>second
> > sensor, and not find it, and that would cause problems. That is
>considering
> > the engine would even start, which I doubt it would. If pin #7 is not a
> > ground on the Jetta ECU, then there's your answer. I guess the only way
>to
> > know for sure is to try it. I'm too scared.
> > -Mark
> >
> > >From: tmiller <tmiller@VCMAILS.COM>
> > >Reply-To: tmiller <tmiller@VCMAILS.COM>
> > >To: vanagon@GERRY.VANAGON.COM
> > >Subject: Actual Vanagon content!!
> > >Date: Sun, 25 Apr 2004 19:10:53 -0400
> > >
> > >Has anyone tried to use a Digifant ECU for the same year VW Golf or
> > >Jetta?  I was specifically curious about the use of an 89 1.8L Jetta
>ECU
> > >in an 89 Vanagon.  The controls are similar, the sensors are similar,
> > >has anyone tried this?
> > >TEMiller
> >
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>

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