Backfire on decel (assuming this means foot off the gas pedal) generally
means that your throttle switch is not closing properly or the signal not
being seen by the ECU.  ECU totally shuts off the fuel when throttle is
closed and rpm above 1500, and turns it back on when it gets somewhere down
around 1000 IIRC.  The engine is literally not running at this point.

Note that the closed-throttle and full-throttle switches (separate switches
through sometime '85) send the same signal to the ECU which consults AFM to
determine which event is going on.  So it's at least conceivable that it
might get confused and richen the mix instead of shutting off entirely.  I
bet it's very very hard to make that happen though.

d

At 10:44 AM 11/25/2003, Owen wrote:
>My 84 backfired occasionally on deceleration when I first got it. There were
>exhaust leaks everywhere with the worst at the union. Replacing the O2
>sensor and getting a better seal at the union reduced the backfiring
>considerably. Since then I have tightened up the other leaks due to stripped
>studs and the backfiring has disappeared.
>
>----- Original Message -----
>From: "Hans Vanhethoen" <hvhus@YAHOO.COM>
>To: <vanagon@GERRY.VANAGON.COM>
>Sent: Tuesday, November 25, 2003 5:56 AM
>Subject: Re: Timing how to.
>
>
> > I would check real good for exhaust leaks first as my 84 does backfire
> > because I have big holes in my exhaust now and am replacing in the near
> > future, I might make mine out of stainless or mild steel sometime this
> > winter when I have time. Good luck.
> >

--
David Beierl - Providence RI USA -- http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"