Hi all, I'm quickly running out of ideas with my 1989 S124 200TE M102.


Basically it starts misfiring that gradually gets worse as it warms up to the point it just cuts out, the plugs are horrifically fouled and it plumes out white/grey toxic smelling smoke that gradually gets worse.



My initial thought was leaky injectors as the engine oil smelt contaminated with fuel and it was very thin and runny, changed all four injectors for new genuine Bosch and no change!


Considered that the valve stem seals were allowing the very thin fuel contaminated oil into combustion chamber and mimicking rich running hence the fouled plugs and consistent white/grey smoke so today I replaced the oil with some much thicker 20w50 oil hoping for atleast a slight improvement but again still the same!(although oil pressure now looks better)



I should also mention that I've checked the function of the cold start valve and it seems to be working as required, a squirt of fuel on cold start for about 1 second.



Have checked the vacuum line from the transmission modulator and no sign of any fluid making its way into the inlet manifold.



Have carried out a sniff test which it passed, it doesn't overheat, lose any coolant or have any sign of coolant mixing with oil/creamy filler cap.


Have replaced the distributor cap, rotor arm, plugs and leads for genuine Bosch and NGK parts.


It did appear that the air/fuel screw had been fiddled with previous to me getting the car so I've managed to adjust it to the point that there is around 2mm of free play in the air flow plate and the thing will actually run for at least 10 minutes before it eventually misfires and dies presumably due to the fouled plugs. I'm unable to adjust duty cycle as mine is a pre-CAT and has no O2 sensor.


Anyone have any ideas what I could be looking at next?
If the air/fuel mixture is still way out of adjustment and set too rich could it be that far rich that it spews out plumes of white unburnt fuel and fouls the plugs? I know it does burn small amounts of oil from the valve stem seals but that appears to be seperate to the white/grey smoke...


I should also point out that this is a project car and is currently not on the road...


https://youtu.be/_8jLZuK_UzY?si=FdjyyABSlsbbO_yj - Video showing smoke and rough running engine



https://youtu.be/I1NtgKmoISE?si=JqgK44rxBy-MtlrD - Video showing smoke, note the black soot mark left on the grass!



Many thanks for any advice
Steve