M103 Misfiring/fouled plugs issue.... - Page 2 - PeachParts Mercedes-Benz Forum

pawoSD · #1 01-09-2009, 07:26 PM

Our 300E seems to be having an issue with fouling the plugs.....

I pulled the spark plugs a few days ago and the plugs from cylinders 1 3 and 6 were pretty coked/fouled up with carbon and slightly oily. #6 was by far the worst, the entire electrode/gap was completely coked over... I attributed this to it running rich up until I solved its idle control issues. (had it running mechanically with stuff unplugged for about 700 miles or so) So I cleaned them, re-gapped them and put them back in....ran great. Now its misfiring again, only a couple hundred miles later. On top of the misfire, when you turn the car off, an oily smoke/mist emits from the exhaust pipe. It smells like burnt oil/gas. I'm assuming its oily gas burning off in the exhaust from the misfiring cylinder(s)? It really doesn't use all that much oil....we've driven it nearly 1800 miles since I did an oil change on it with M1 0w40....and I've only added maybe 1.2 qts to keep it near the top. Should I use a different (thicker) grade oil to combat oil burning/leaking?

Tomorrow I am going to pull and inspect the plugs again as well as swap the distributor rotor and cap with new ones....the previous owner(idiot) ran resistor plugs in it, who knows what that did to the distributor...

Any ideas? It doesn't seem to have a head gasket problem....coolant is clean and the oil looks fine..no overheating or pressure in the hoses....so there's no mixing going on or anything, and no coolant is lost at all.

Engine only has 135k on it....