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  #1  
Old 04-06-2005, 04:39 PM
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Join Date: Apr 2005
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Unhappy Rough idle

I have a '79 450 SL with about 140K on it. It's been well maintained and recently been tuned and a new timing chain. It has developed a really rough idle, but it's not consistent. Sometimes it runs well, but most of the time it's very rough. Gets a little better at normal op temp. Basically, it idles so rough it feels as if it will stall. When I hit the gas to accellerate, it runs great. In neutral it idles great. Problem seems to be at idle under the load of being in gear. Once it's warmed up it's better, but not perfect. Seems to miss eratically at idle, but again, once I accellerate it seems to drive well. Any ideas. Help and thanks.

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  #2  
Old 04-06-2005, 05:59 PM
Ta ra ra boom de ay
 
Join Date: Jun 2004
Location: Pittsburgh
Posts: 1,915
Search spark plugs.
What kind of non copper plaitnum's did they put in it?
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1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/showpost.php?p=831799&postcount=13
http://www.peachparts.com/shopforum/showpost.php?p=831807&postcount=14
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  #3  
Old 04-06-2005, 06:23 PM
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Join Date: Apr 2005
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I'll have to pull one and look. I think they may be Bosch, but I'm not sure. Thanks for the thought.
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  #4  
Old 04-06-2005, 07:37 PM
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may or may not be related. se below.


http://www.peachparts.com/shopforum/showthread.php?t=5236&highlight=rough+idle+450
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  #5  
Old 04-06-2005, 10:57 PM
88Black560SL
 
Join Date: Oct 2004
Location: CT
Posts: 3,535
This sound like ignition cap rotor wires coil etc. Try not to drive the car too much until you get this sorted or you may loose the catalitic converter. Does the place you had it tuned at have a scope. Or might you have spares you can swap out.

John Roncallo

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