Cracked Exhuast Manifold

I have a very poor running M110 in my '77 280E.Cannot be driven more than 5kph. I've been checking everything in the Fuel System(K-Jetronic) And today I have just found a Decent size crack in the Exhaust Manifold
where the front and Rear manifold merge into 1 pipe.
Could this be my problem? Rough idling,Sputtering,Will not Rev, Stalling?
Thanks Jeremy
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Will this Cause the Engine to run rich or lean? And would it effect Vacumn at all?

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A crack in the exhaust must be quite NOISY!!!
It would not affect the engine's vacuum at all BUT could be a sign of why the engine has no power. Given the symptoms of poor running, no power and only minimum engine speed I'd suspect the exhaust is plugged and the engine can't discharge its exhaust gases. Its choking on its exhaust.
I'd check the exhaust pipe from the engine backwards to the rear bumper for damage. Could have driven over a rock that bent the pipe flat. Or the catallic converter - if there is one (my '79 280E had four) has collapsed and now the debris block the exhaust. You begin to see the possibilities.
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It's only a small crack so it's not to loud. A bit fumy though.
I think the crack in the manifold may have been caused by a loose Exhaust system. All the pipes seem to be undamaged.And I don't think I have any cats!
I'll see if I can find a Replacement Manifold piece or maybe just weld it.
If that doesn't help the engine run properly.I'll have to keep troubleshooting the fuel System.
Thanks for you help.

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I think the control pressure may be too high,which in turn limits the travel of the control plunger inside the airflow sensor.Also is the fuel pump shut-off switch on top of your airflow sensor good?It is blue and points toward the head directly on top.
Also with the engine not running,press down on the circular plate on the airflow sensor to see if it binds on the way down and up.
Many other variables could cause this problem on K jetronic.
I host a 116 forum at benzworld and I have a D and K jetronic troubleshooting thread that may prove quite useful to you and I did it in quite exhaustive detail if you are interested.
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easily hear it, especially under load.

BMW had none from the factory...

Let us know, Marty
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man ... I have been learning a lot from you guys, even about how rocks can damage the exhaust manifold, Even though it is serious, I try not to laugh about it when I read your posts- I like the way you write them, they are comical to read- how some cars can really get messed up.
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