When the ignition is turned on, the idle control valve on my '93 190E 2.3 operates for 10 seconds then turns off. After the car is running, there is no change in idle speed if I unplug the ICV. When the car is warmed up for 2-3 minutes it idles and drives perfect. But, when starting it cold, it seems like the Idle Control Valve is limiting vacuum to the air flow plate and there is no vacuum at the Ignition Control Module until after 2-3 minutes. After that, there is vacuum at the ICM and if I unplug the vacuum line at the ICM, the idle drops.
I have all new hoses to and from the ICV and I removed it and gave it a good cleaning. It has a slight opening with no power applied.

The engine used to start up immediately and idle at 1000 rpmsfor a couple of minutes and drop to 7-800 rpms. Now during cold start-ups, I have to press on the accelerator for a couple of minutes until the rpms start to increase.
The OVP relay and fuse appear to be OK.
So my question is, is the Idle Control Valve supposed to remain operated during the warm-up stage, and then release or what??? If I apply voltage to the ICV it clicks and fully opens. But it doesn't appear to be doing anything during the start-up or even later when the engine is at operating temperature.

Any ideas?
Crank Position Sensor?
Coolant Temperature Sensor?

Thanks,

Dave

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1993 190E 2.3
2001 SLK230
1971 LS5 (454) Corvette Convertible

"So my question is, is the Idle Control Valve supposed to remain operated during the warm-up stage, and then release or what??? If I apply voltage to the ICV it clicks and fully opens."


I'm sure as heck no expert on this, but I just got through trying to diagnose one of these on my '86 560SL. If yours is similar in operation, read on. I thought the 'at rest' state of the ICV was wide open, that is, the little air port is fully exposed. On start-up, the idle control unit (behind dash on my car) ciruitry monitors the input from throttle position and coolant temperature, gradually closing the valve to slow the idle speed. So, a short 12V burst should energize the solenoid in the valve, closing it, not opening it. If you cleaned it, and it closes, it works.
Have you checked the idle control box/unit circuit? I resoldered the board on mine and it did help, but the part number that is on it is not the right one for my car, so I'm waiting for one I found on EBay to arrive.

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1986 560SL
2002 Toyota Camry
1993 Lexus

When my Idle Control Valve operates, it is fully open. When voltage is removed it closes to the 'at rest' state, which is slightly open.
It's like something is not telling the ICV to remain operated, or operated enough to let it idle higher at cold start-ups.

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1993 190E 2.3
2001 SLK230
1971 LS5 (454) Corvette Convertible

no voltage to icv and the internal flap is almost all the way closed.
voltage and the internal flap begins to open and 12v and it will flip all the way open with a click. If this all works, you know the icv isnt dead, but that is about all it tells you. The time it is open and the % it is open is controlled elsewhere. have you checked yout engine/water/coolant temp sensors. They play a part in when the icv begins to open or stays shut.

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Christopher Henkel
1990 190E 2.6 - Arctic white SOLD
1986 190E-16v - Blauswartze
1993 300CE - SOLD
2003 W208 CLK 320 Cabriolet - Magma Red

Yes, your description matches my current ICV operation. I tested the Coolant Temperature Sensor according to the test procedures and the resistance at cold and rising to operating temperatures appear to be correct according to the resistance/temp chart.
There's got to be more to the ICV operation than just a 10 second burst when the ignition is turned on. And, on top of that, there is no voltage change at the ICV connector when it first operates, then releases after 10 seconds. Maybe an internal thermal circuit?

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1993 190E 2.3
2001 SLK230
1971 LS5 (454) Corvette Convertible