I've been doing some reading and wondering about the butterfly valve on the 123's. I know at least the EGR equipt ones had the butterfly valves but did the older ones as well? The reason for asking; I was going to remove it on my 82 240D (already disabled the EGR), but I wondered for a second if it would increase the possibility of a runaway? So if the older ones ('81 and older i think) didn't have it, did they have more instances of runaways to anyone's knowledge?

There is a vacuume check valve in front of the valve cover also, what does that valve "indicate" to the EGR in its operation? And the metal valve on the passenger fender ... is that just a one-way valve? I was going to remove all that and the black box anyway (standard transmission) to make it easier to work on the vehicle, but I was just curious about the vac lines and most especially the butterfly valve it having anything to do with engine protection.

Thanks

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'82 240D 224K miles manual transmission
mods: wooden 4by4 bumper, EGR delete and older EX manifold without EGR port, glass pack muffler (cheapest replacement muffler), rebuilt bosch injectors with Monark nozzles

working on: aux electric fuel pump, coolant/fuel heat exchanger/filter head, afterglow, low oil pressure buzzer/LED

It has nothing to do with runaway. The butterfly just restricts fresh airflow to let exhaust gas get sucked in instead. It doesn't close completely either so I don't think it'll help prevent a runaway either.

The euro cars did just fine with no butterfly valve.

but what does that vac valve in front of the cam cover do? i know it basically turns the egr on and off but what does it run off of, what controls it? temperature or pressure from somewhere?

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'82 240D 224K miles manual transmission
mods: wooden 4by4 bumper, EGR delete and older EX manifold without EGR port, glass pack muffler (cheapest replacement muffler), rebuilt bosch injectors with Monark nozzles

working on: aux electric fuel pump, coolant/fuel heat exchanger/filter head, afterglow, low oil pressure buzzer/LED

It runs off the pedal position. Open the black box on the cam cover, you'll see this plastic cam that opens and closes those little valves depending on how far the pedal is pressed.