I've noticed that the butterfly valve at the intake keeps opening closing a lot when at idle. With it opening and closing you can hear a change in the sound of the engine constantly. Is this normal? I've never noticed it before.

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1996 E300D

Is this on your 96?

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Is this only when the engine is below operating temperatures?

Yes it the 96 and it does it the whole one the engine is running. Cold or warm

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1996 E300D

I've never noticed it opening and closing that much until this week. I decided to ask on here if that was normal or something I needed I have looked at.

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1996 E300D

Hello,
I have been stumped by this valve for years and today will be solving the problem for good. Jeremy5848 has a good solution in a posting from 2012
http://www.peachparts.com/shopforum/diesel-discussion/318935-om606na-1996-97-pressure-control-flap-removal.html?highlight=om606+pressure+control+flap
He has the opinion that the valves purpose is to lower the pressure in the intake in order to suck more exhaust gas into the "lungs" through the EGR. Therefore if you have stopped the issue with the tar buildup in the system the valve serves no purpose.

The butterfly valve actually controls flow rate. The volume of air/exhaust gas mixture is constant based on cylinder volume but the mixture ratio can vary dependant on the butterfly position. The main purpose of introducing exhaust gas to the combustion chamber is to reduce the oxygen content thereby reducing combustion temperature. This in turn reduces NOX or cleans up emissions and at the same time reducing miles per gallon.

Just wanted to clarify the thought process of installing it in the first place.

Thanks for the info. Do I need to do anything about it opening/closing so much?

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1996 E300D

http://www.peachparts.com/shopforum/diesel-discussion/345280-96-e300d-surging-missing-after-filter-replacment-2.html

If anything the sound it makes is annoying. Hard to describe.

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1996 E300D

The amount of opening and closing is based on theoretical calculations programmed in the CPU not much you can do about that. Lots of people disable it however and lots of engine benefits from doing so.