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egine rough at idle.

Started by Rob Smith, 21 May 2022, 04:43 PM

Rob Smith

I'm having an issue with my 1973 450se. When started cold, idle is really rough sounds like a few plugs not firing and #4 and #8 plugs sooty. The temp gauge is erratic and doesn't seem to move any.   I haven't let it warm up because it's too rough. Any help would be appreciated.

Thanks

s class

Djet is notorious for running rich when cold, which leads to the fouled plugs.  You can try leaning it out a bit at the ecu and/or mps.  You could also try going one heat range up on the spark plugs.  A contributor often is a tired AAV that isn't giving enough additional idle air when cold.


[color=blue]'76 6.9 Euro[/color], [color=red]'78 6.9 AMG[/color], '80 280SE, [color=brown]'74 350SE[/color], [color=black]'82 500SEL euro full hydro, '83 500SEL euro full hydro [/color], '81 500SL

Jay Gibbs

Could be gummed up injectors too. My 75 450SL had d-jet morning sickness. Removed the injectors and sent them off to Witch Hunter for testing and cleaning. Cost was less than $200.00 with very good results. Also helpful was slightly leaning at ECU. Combination of results was an overall smoother running engine as well as going from 8mpg to 12...

J.G.

oscarDJ

Is there a thread related to leaning the injectors at the ecu? I've just got my injectors reconditioned this might help get it running