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#1
10-20-2008, 03:41 PM
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'77 450 Rough pulling at Low-Mid RPM
Hi All,
I have my Dad's 77 450SL (48,000 miles) for the winter to do a little work on it for him. It starts easily, hot or cold, and seems to run nicely with plenty of power once you get over 2500 RPM, but getting there it is quite rough and lacks power. He had a shop replace several injectors a while back, but he said that made no improvement. Seems to be getting plenty of fuel - rich if anything. Vacuum seems to be within specs, and spark looks consistant to all cylinders. I have a good bit of experience with older cars (mostly MOPAR), but none with Mercedes. I do have the shop manual (CD) and Haynes book. Lots of similar threads out there mention the CAT. Thoughts? 
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#2
10-20-2008, 10:08 PM
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It sounds like you have a lot of carbon.With 48k in 31 years it is easy for
that to build up with inactivity.What you may want to try is a can of BG44K,this is a very potent combustion chamber cleaner.I used on my low mileage 77 450sl and it helped smooth it out.Most high end auto dealers carry this. Good Luck
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#4
10-24-2008, 06:08 PM
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I suggest checking the timing and advance, especially the vacuum advance. When you hit the throttle, you should see a shot of quick advance, and then it should go up to 42 degrees or so at 3000 RPM. This could also be a mixture problem - no enrichment on acceleration. Be sure both sides of the warm-up regulator hold vacuum. Also check that the sensor plate moves up and down smoothly.
__________________
Chuck Taylor Falls Church VA '66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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