Idle way too high - Mercedes-Benz Forum

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post #1 of 5 (permalink) Old 03-31-2013, 01:50 PM Thread Starter
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Idle way too high

I started by 71 220D and the idle is way way too high. Also I had oil all over the engine.

All I can think of is the intake manifold was out of place and I tightened it.

If you can help please help.
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post #2 of 5 (permalink) Old 03-31-2013, 04:35 PM
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Check the governor line leading from the intake manifold to the rear of the injection pump. If it's the old plastic style they can be fragile and will break easily.
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post #3 of 5 (permalink) Old 03-31-2013, 06:01 PM Thread Starter
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I checked that and it seemed okay. I loosened the bolt to the intake manifold and now the idle is fine but I don't understand why the bolt to the intake and exhaust makes that kind of a difference.

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post #4 of 5 (permalink) Old 04-04-2013, 02:35 AM
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A high idle on a 1971 220D is mostly caused by an air leak. Your diesel pump is governed by a vacuum created by a venturi in the intake, the air line transfers that vacuum to the governor on the pump. Loosening or fastening bolts on the intake manifold changes the amount of air sucked in through past the venturi.

Read here for a description of how the system works:
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post #5 of 5 (permalink) Old 04-05-2013, 07:54 AM
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disconnect line from vacuum pump to intake , temporarely plug intake , start car , i ll bet you will see oil coming out of line , in this case replace diaphragm in vacuum pump at front of engine .
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