w116 running lumpy - Mercedes-Benz Forum

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post #1 of 4 (permalink) Old 09-15-2015, 01:28 PM Thread Starter
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Unhappy w116 running lumpy

Hi Everyone my first post ever on any forum, hope someone can help or point me in the right direction.
My lovley w116 280sel 1978 isnt running as it should. Ive had several other old Mercs but this is my first w116. It is running lumpy and groggy. Several garages have sorted it temporarily but it always goes back lumpy after a few weeks / couple of months. Its like no one can sort it once and for all. They have all said it runs lean and made various adjustments to fix it but always goes back to the old lumpy runner. It is like every time I come to a junction and idle, or do a three point turn it wants to cut out or does cut out, sometimes after about 30 mins it kind of runs good for the day. Some mechanics have siad the leads, sparks or distributor. Like its misfiring. Do not know what to do please help.
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post #2 of 4 (permalink) Old 09-15-2015, 01:51 PM
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Hmm... M110 not running well at warmup? Runs too lean? Maybe AAV is stuck and it doesn't get enough air on startup, but too much once warm. The AAV is hard to get to on the m110 engine. I think it requires removing the intake manifold. Maybe that's it. Maybe it's other stuff.


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post #3 of 4 (permalink) Old 09-17-2015, 03:50 AM
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The earlier 116 had D -jet at some point the switch was to K- jet fueling .mid 70's?
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post #4 of 4 (permalink) Old 09-17-2015, 10:51 AM
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1976 and up had KJet.

Have the shops checked it for vacuum leaks? There are hoses under the intake manifold that can crack and cause vacuum leaks. Best thing to do is a smoke test of the intake system.

Chuck Taylor
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