Hello all, I myself have a problem with my 1974 450SL running rich. I noticed this from the new spark plugs I changed covered in black soot.

I’ve read this entire thread and I’ve pretty much done all I can think of when approaching the problem and trying to deduct what it could be. Fuel pressure is normal at 29psi, new fuel filter, new fuel injectors with all new rubber seals all matching and all correct (part number for injectors is 0 280 150 036).

I recently took it to a ford dealership where they did a tail pipe test and the numbers read CO 11.59% and CO2 is 6.1%. I know the range is 0.5-2% range and the O2 is 1.9%. When I was there I turned the knob on the ecu completely to the left:counter clockwise and the values went up! So maybe counterclockwise depends on how you orient yourself when facing the ecu unit. Does that make sense?

Timing is set to 5* atdc like the black plaque on the radiator support frame states and the idle sets at around 700-800. I set it to around 750 or so in the middle of the range.

I’m not sure if it a vacuum leak or something. I’ve adjusted the regulating linkage to the numbers they give in 7.4-300 of tonk.ca website which has what I believe to be the entire service manual online.

So right now I’m at a loss of what it could be.

I’ve even turned the knob on the ecu under the passenger footwell completely to the left which is counterclockwise to lean out the mixture.