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Hello, I have been on the W221 platform board for a couple years. Have both learned and helped.
I have a 1976 4.5 liter. It's a summer driver for me in Wisconsin. Have had it for 20 yrs. this month. Wholly upside down in it, but, welcome to old MB's, I guess. The engine is the newer injector models, not the original, hard to deal with ones
Have a good mechanic, but he cannot fix the high idle (2200 rpms after start, while static). We have the plastic mixture control screwed down tight. He replaced the rear gasket near the firewall, which he said breaksdown and leaks. Good chunk of money spent w/o a fix. We've messed with vacuum lines to hell and back and still high idle.
Spooky part is it's sproratic. Sometimes it'll sit in the 8-900 rpm range, as it's supposed to. Other warm weather starts it'll go to the 2200 range and stay. I hate putting into gear, as the hit on the transmission cannot be good. Occasionally, albeit it rare, I have to keep the accelerator pressured to keep it idling or it idles like it has an old 3/4 quarter race camshaft from old dragster days.
I know there are more potential things to look for and solutions than hair on our head, but anyone have this issue? What's helped and what is the first to look for?
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