Re: 86 5kCSQ jerks when deacclerated

[paul.heneghan@bbc.co.uk (Paul Heneghan)]

From: ihusain@pyramid.com (Intisar Husain)

>> I saw another post on the decel shutoff valve

> It only happens when I removed the foot completely off the
> throttle.

>> The decel bypass
>> is only enabled if the RPMs are above a certain value and the Idle
>> Switch is closed.

> The normal scenario for the jerk is while I am going around
> 20MPH, in 2nd gear, bar about 0.4 to 0.7, and if I take off
> the foot completely.

<snip>

My 1989 Avant has a dashpot on the 1st stage of the throttle presumably to 
prevent it snapping shut too quickly.  Even still, on cold mornings, there 
is a jerk if I slow down to a standstill in second gear within the first 
couple of minutes of driving.

Once the car warms up, the dashpot makes it behave smoothly.

>My car idles around 1250 RPM, I am not sure if it is normal.
> I have ordered the service manual, and will look into this.
> By the way what is decal bypass?

An economy measure.  It allows the air measuring flap to return to rest 
quickly so that the petrol being injected is minimised.  It only occurs if 
the revs are above a certain amount with the throttle closed.

Paul
paul.heneghan@bbc.co.uk
1984 Audi 80 quattro
1989 Audi 100 Avant