Hi, thanks for the response. Let me give you some more info, see if you can help.

Car's a 1987 300e manual, no catalytic converter so no lambda, or closed loop operation I guess. Haven't looked but doubt there's an O2 sensor either. 160,000 km. Bought it 8 months ago and these idling problems started after I replaced the fuel accumulator to cure a hot start problem. Injectors were replaced at same time. Have changed OVP, Fuel Pump and AC relays. Fuel pressure regulator looks newish.

The problems include fluctuating idle, stalling when decelerating to a stop, the very occasional momentary loss of power under acceleration. They appear intermittently, which is making it hard to figure out what is wrong.

The only parts I haven't changed yet are the idle control valve, which I believe is stuck, and the air sensor potentiometer, which I swapped and swapped back with another unit.

Hot start is fine, cold start was fine until yesterday when it started playing up. Takes two or three cranks and a tickle on the gas to bring it to life. This has been accompanied by the return of stalling problem, intermittent 500rpm low idle when warmed up, occasional fluctuating idle.

My mechanic, who actually works at the local dealership, comes round at weekends to tinker. His experience is with new models so its a lesson for him with KE equipped cars.

When we have the air filter box off, we watch the throttle plate occasionally deviate as the idle fluctuates. He adjusts the idle by fiddling with the mixture until it stabliises to around 750. Blips up then stablises again when AC or PS load is applied.

The ICV was cleaned and both hoses replaced - one was cracked - when I swapped out the pot. This cured the problems for a week but then they came back.

Swapped back the pot last weekend as thought unlikely to be at fault and focussed on ICV. Removed and reconnected and tried KOEO, no movement. Looking at the slide inside the unit, which appears worn BTW, it is open about 1/4 way.

There is power at the connector so would expect the valve to close, as per previous posts. As there's no movement I conclude that it is jammed and needs replacing, which is fine. At $90 I'm OK with that.

That said, would a jammed ICV cause the symptoms I'm experiencing?

If I replace with a new one, is it OK to adjust the idle with the mixture screw? I plan to try the tip of estimating the mixture using a squirt of carb cleaner. I presume that without the closed loop situation, checking the EHA current wouldn't help.

Of course in the perfect world, I'll change the ICV and everything will work perfectly without adjustment. So any tips on setting the idle and mixture without access to CO analysis would be fantastic.

TIA for your advice and info