560SL stumble when cold started
 

I've had the car about 1 month and noticed that when cold, upon startup the engine would "shake and sputter" for 2 - 3 seconds as the idle initially went to about 1200, then settled down to 650. It never felt like it was going to die, just was rough.

I had been under the hood anyway so I decided to peek under the distributor cap. There was a small dusting of carbon around the rotor contact which I cleaned off with a rag. The 8 cap contact points looked OK, but the leading edge of the rotor was burned and pitted. Not like there were 1 mm pits on it, but there were some high points (looked like 80 grig sandpaper) and carbon blackening. I dressed the edge with a file and some sandpaper and reinstalled.

Now I have no idea if the effect was directly related or not, but the idle smoothed right out when I restarted cold. It had been sitting for 3 days while I did some other repairs. Other posts talk about this problem going away as the car sits for a few days. May be related to particles clogging the intake screen to the fuel pump. After driving for a few days I'll repost if the problem returns.