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Re: Erratic Idle
Posted by Markus Jaervi (more from Markus Jaervi) on Sun, 4 Mar 2001 10:39:22
In Reply to: , Kok Chen, Sat, 17 Dec 1988 12:00:00 

My -92 9k CSi had a rough idling problem especially on cold mornings.
The problem turned out to be basic idle. Practically all of the air on
idle was flowing through the AIC valve and on cold mornings the valve
ran out of air delivery capacity. To keep the engine running the mixture
was enriched which resulted as rough running.
The critical point is that the car is equipped with LH Jetronic 2.4.2
injection system. This sytem was present on naturally aspirated 2,3
litre engines manufactured between 91 and 93. This system uses the three
connector AIC valve and a throttle position sensor (instead of switch).
The basic idle adjustment for LH 2.4 or LH 2.4.1 does not apply.

I did not find a basic idle adjustment procedure for LH Jetronic 2.4.2
iso I'll explain it here.

1. Adjust the intake butterfly so wide open that the engine was running
well above idle
2. Restart the engine and watch the tachometer - the LH ECU adjusts the
idle to 850-900 rpm every time the car is started
3. Repeat steps 1 and 2 until rpms won't fall under 1000 - the butterfly
is so wide open that no air is flowin through AIC valve
4. Back up the adjustement screw so that a bit of air flows through the
AIC valve - now it has capacity to increase airflow when needed
5. Restart the engine and checkk it's idling at 850-900 rpm

Markus Jarvi
-92 9k CSim
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