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  #1  
Old 03-20-2009, 11:34 AM
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420 SEL running rich

hi all,

finally got my 86 420sel running (had to replace camshaft, did timing chain, rails, etc.). when i pulled the plugs they were all covered in soot (from running too rich, not oil) when the engine is warmed up there is a fuel smell from the exhaust, also has a rough idle (idle is steady at 650 rpm but the engine is shaking a bit) also it seems that it has no power. so i am wondering what would cause it to run rich...would an air intake leak cause it to run rich? i am planning on checking the mixture via the x11 connector later this weekend and also replacing the o2 sensor. I don't think it would be an injector since all cylinders are running rich; any input will be appreciated

thanks

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Old 03-20-2009, 10:10 PM
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anyone? well today i was sitting at a stop light and decided to pump the brakes...when i pump them the idle smooths out; so i am thinking it's got a vacuum leak somewhere....does that sound right?
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Old 03-21-2009, 08:44 AM
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If it is running rich then a vacuum leak would cause it to run better. Pumping the brakes (vacuum operated) would effectively cause a vacuum leak, therefor it runs better. I would be looking for a temperature sensor not connected or not making a good connection. Also there are many threads explaining how to adjust the mixture. Do a search.
Paul
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Old 03-21-2009, 10:07 AM
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Did you check the cam timing marks with the tensioner installed?
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'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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Old 03-21-2009, 03:20 PM
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yes timing marks are dead on after new chain was installed
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Old 03-23-2009, 11:00 AM
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i adjusted the lambda; when i checked it it was showing around 80-89% duty cycle. i adjusted it down to 45-50%...idle's great now...can't even tell the engine is running when i am inside the car....thanks for all the replies

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