HEy techies,

I have a '72 350SL 4.5 ( Yes it really is a us 450sl) same engine as the 450sl. 140,000 miles

It has started to have a rough idle ALL THE TIME.

All 8 Spark plugs foul up with a Black Soot, Like Black Smoke.
I have been told this is an indication of a Rich Fuel Mixture.

I have replaced most of the hoses, I have replaced the Fuel Pressure regulator, Spark plugs are new, Spark plug wires are new, I replaced the Fuel Filter, The Heater Valve Sensor, the Engine Temp Sensor.

What should I be looking for? The mechanic that I had look t it in Lubbock, TX suggested an engine overhaul at $4,500. I don't really think I need that. So I am having my father work on it, He has repaired cars for 40 years, this one has him stumpded, and I can't get this to my regular mechanic in Dallas.