I am still getting the kinks out of my '85 Euro 280se (W126, M110, 5spd) and have come a LONG way. To refresh this car has only 91k, and sat for a year neglected before I purchased it. After replacing the fuel pump, accumulator, hoses, plugs, filters etc the car was completely driveable but with a hesitation and occasional miss, aqnd a strange problem that caused the car to nearly die after about an hour of driving but a quick key off and key on would make it run for another 20 minutes or so. After 20 minutes, repeat key procedure and keep driving. The car also has a light smoke from the tailpipe which I have yet to find the cause for, and fails the emmisions test here in Texas with a high hydrocarbon reading (I got it down from 1500ppm to about 600ppm by tuning the FI screw on the k-jet).
Latest changes to the car are a new exhaust from cat back (cat & O2 sensor are next) and a high performance ignition setup from Perma-Tune (This cured the key trick problem and smoothed the car ALOT!) but I still need to properly tune the k-jet on this car. The car has a diagnostic port on the drivers side wheelwell but I have found no info on the procedure to tune this car properly. Does anyone have a procedure for this??? I recall somwhere seeing that using an multimeter on 2 pins of the diagnostic port would give a voltage reading to calibrate the air / fuel mixture. Is the white plastic adjustment screw next to the distributor for idle speed or does this control the air mixture? Any an all help appreciated!