'89 740 Idle speed

[Bill]

There is so much on this on the web I have totally confused myself. My car
(B230E engine) idles at a fraction over 1000rpm. I don't think there is a
fault as it is rock steady and idles smoothly, hot or cold, and starts
perfectly.

From what I have read it ought to be idling at about 750-800rpm. From
reading it appears that adjusting the idle involves more than just twiddling
an adjustment screw, but then most of what I have read involves US spec cars
with a different system to mine. I have the CI system with no complicated
black boxes to mess up (according to the Haynes manual).

Is this a job best left to a garage who have gas analysis equipment.

Bill
UK

 

[Tim..]

There is so much on this on the web I have totally confused myself. My car
(B230E engine) idles at a fraction over 1000rpm. I don't think there is a
fault as it is rock steady and idles smoothly, hot or cold, and starts
perfectly.

From what I have read it ought to be idling at about 750-800rpm. From
reading it appears that adjusting the idle involves more than just twiddling
an adjustment screw, but then most of what I have read involves US spec cars
with a different system to mine. I have the CI system with no complicated
black boxes to mess up (according to the Haynes manual).

Is this a job best left to a garage who have gas analysis equipment.

Under the throttle body there is a large knurled knob. Screw this in to
reduce idle speed. You may have to have your CO value adjusted slightly at
next MOT as a result of this. If it makes no difference or idle speed is
variable, then either the auxilary air valve is leaking, or the throttle
body needs cleaning / resetting.

Tim..

 

[Bill]

Under the throttle body there is a large knurled knob. Screw this in to
reduce idle speed. You may have to have your CO value adjusted slightly at
next MOT as a result of this. If it makes no difference or idle speed is
variable, then either the auxilary air valve is leaking, or the throttle
body needs cleaning / resetting.

Thanks Tim, I'll have a play tomorrow.

This is a car I picked up cheap and am gradually working through the various
systems and getting it back in good order.

Bill