help need quickly. My 450sl is idling bad I've tried everything I can think of.
 

Help. I am so frustrated with this car. I can't get it to idle well. I replaced the fuel filter, spark plugs and wires, fuel injector seals an O-rings, distributor cap and rotor, thermovaccum valve, Air valve, set the timing to TDC according to my maintenance manual checked all vaccum lines for leaks. The car runs fine at higher rpms, at idle~800 rpm's when warm it shudders lightly in P or N. At a stoplight in D it shudders so bad it almost stalls. If I set the timing to 20 degrees ATDC it idles faster but not smoother. I need to take this car on a trip soon and have to get it running better. any suggestions?

Dirty throttle body?
 

I'm not too familiar with your car...does it have a throttle body? It's quite common to have throttle bodies build up deposits around the butterfly valve that chokes off the air flow, resulting in poor idle on a car that othewise runs fine. If this is your case, the throttle body bore and valve need to be cleaned with solvent and a toothbrush. The deposits won't "melt" off - they need to be scrubbed well. Clean until you can see an even ring of light around the closed valve when backlit with a strong light.

I second Kestas. I had an american car with this trouble. Eventually it got so bad that it shut off at idle.

ps: How about motor mounts? Mine were toast at 130k and made the car shake. They are not expensive to buy or have put on.

Stevebfl has posted recently about setting the timing on a 450 SL.

Do a search under his username and it should come up.