Can someone help me solve a rough running 300sel problem. To me it looks like an elect. glitch somewhere. Car runs ok on idle (misses just a bit) but when stepping on gas it gets progressively worst to the point that engine won't spin over 3000rpm (backfires, coughs .....). Brand new spark plugs, wires, distributor and rotor plus lambda sensor installed. It helped some but not much. Using M-B, I checked ignition system: timing is ok with cold and warm engine, dwell angle looks to be ok (30), vacuum advances ign. as req., ign. coil seems to be ok. One thing I noticed during timing check with timing light was that as engine was missing timing light was skipping/missing too. As rpm were approaching 3000 engine was stumbling and timing light was "to". Is this a bad coil or ignition module? Also there
is a lot of black sod coming out from exhaust pipes.
Thanks in advance for any help.
Derek
89 300sel 200K

Have you boosted your car lately? This is just a suggestion but you may want to have a look at the fuse under the hood. It is located behind the firewall appx. in the center. It is a little fuse cover. Open it and check it. You probably have already but if this is blown the engine will run very rough.

Fuse is ok, actually overvoltage protection relay is brand new with two fuses on the top.

Can someone give me educated suggestion, should I go after a ign. coil or main module?