RE: Deceleration

[Aleksander Mierzwa <alex@matrix.com.pl>]

Mike,
All the symptoms seem connected to me. When you let off the gas and the
engine rpms are above certain value (1200 if memory serves me right),
the ECU is supposed to cut off the fuel supply. There's a device called
"deceleration fuel cut-off valve" on the fuel distributor. When it's
working, there's no fuel coming into the engine, so the instant mpg is
0, that's why the computer shows "---". It seems like you have a problem
with idle stabilization system. If the engine idles at 1800rpm, the fuel
cut off isn't activated (that's why the computer shows the same
consumption as on idle) and the engine braking effect is reduced. I
would start with checking the idle switch - it often works
intermittently. Cleaning the ISV with carb cleaner is also a good idea.
If this doesn't help, the problem probably lies somewhere deeper in the
electrical systems, but I'm not too familiar with 80s. Hope this helps.

Aleksander Mierzwa
Warsaw, Poland
mailto:alex@matrix.com.pl
87 Audi 5000CS turbo (mine)
88 Renault Medallion wagon (mom's)
91 mountain bike (just in case both cars broke at the same time :-)

> -----Original Message-----
> From:	Martha Stump [SMTP:tree@triton.net]
> Sent:	Wednesday, January 14, 1998 6:53 AM
> To:	Quattro List
> Subject:	Deceleration
> 
> My '89 80 quattro is having a very strage problem.  When I let off the
> gas to decelerate (or after downshifting), my trip computor, when set
> on the instant mpg, will normally only show dashed lines.  However,
> occasionally it will show the same mpg that the car would get if I
> took it out of gear.  Accomponying this is a serious lack of engine
> braking.  There's no reason that I can tell as to why this happens
> (the car seems to be randomly annoying me) and in addition, my car
> will sometimes idle anywhere from 1100 rpm to 1800 rpm (normal is
> about 800).  Any ideas on what's wrong or how to fiw it?  Much thanks
> in advance!!!!! 
> Mike Stump 
> '89 80q