Idle screw on NG engine

[Huw Powell]

"In order to get my idle where it belongs, I've had to play with the
idle screw on my Coupe GT (2.3 NG). But somebody told
me that if the engine is tuned properly and there are no vacuum leaks
that the screw should be closed all the way and the
ECU will control the idle. Can anyone confirm whether this is true?"

> Air _must_ pass into the engine at idle. If the throttle plate is adjusted
> properly, it should be nearly closed allowing the idle "bypass" screw to
> "fine tune" the amount of air for idle. The ECU can control the amount of
> fuel and timing advance, not air.

The ECU controls the air via the idle stabiliser valve.  The 87.5 Coupe
GT NG setup still has a "legacy" idle screw - which is not even present
on the later NG's.

As the throttle plates shut, the idle switch is activated, and the ECU
takes over, running the ISV and fine tuning its duty cycle by reading
RPM.  (and also setting the timing to 12 degrees BTDC - just barely off
idle, the timing shoots up to about 45 degrees!)

--
Huw Powell

http://www.humanspeakers.com/

http://www.humanthoughts.org/