high idle

84 500 SEL. Idles around 1800. When the idle computer is unplugged, there is no change what so ever in the idle, at all. Bad unit?

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There are two reason for high idles...
1. Bad idle module... this is verified by doing a MB specified diagnostic procedure and measurement... Simple test is to unplug the air valve wire (not module unit)... if unplugging raises the RPM even higher then see #2.
2. Massive vacuum leak.... most likely is the black vacuum tube... rigid one... on passenger side of the engine. Otherwise, spray carb cleaner to see where engine idle would change (stumbles a bit)
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Well I unplugged the 2 wires going to the idle valve, and nothing happened. So I ran 2 wires from the battery to the valve, and the engine dies when I attach the jumper wires, so I think the idle valve is working fine.
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If I were to buy a new idle computer, is there a specific one for the Euro model?
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Pull the computer out and have the part supplier match the part number.
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