I took my 420 sel to the local MB shop to verify what I thougt to be a blown head gasket. They confirmed #3 cyl. was getting anti-freeze. I took it home for my project. On the way home it ran really ragged, would hardly idle. Going there it ran pretty good except for running warmer than normal. Not sure what happened except their leak testing.
I replaced the head gaskets and did all the top end stuff, resurface both heads, valve work, chain, etc. everything back together and the ragged idle was still there. Took it back to the MB shop to be analized, and make sure I had everything right. The tech. said I had a bad injector in #8. I replaced it, same thing. I have now replaced all with new. A little better but still rough idle and hesitant at low RPM's. It smooths out above 1700 r's.
A long story to get to the point, help, any ideas?

What about the spark plug resistor tips, rotor; dist. cap?

__________________
'91 300SEL

I replaced the wires, rotor cap and button about 1 year ago. The roughness at idle is even and consistant not so much like a electrical misfire. I'm stumped. It's almost like a vacuum advance problem. I have the CD for the 126 model but I can't find any helpful troubleshooting info in it.
Thanks,

Here's another place to hunt for info:

http://www.mercedes.cx/archives/mq.html

__________________
'91 300SEL