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.

Search spark plugs.
What kind of non copper plaitnum's did they put in it?

I'll have to pull one and look. I think they may be Bosch, but I'm not sure. Thanks for the thought.

may or may not be related. se below.


http://www.peachparts.com/shopforum/showthread.php?t=5236&highlight=rough+idle+450

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