Last time I went to take my 220D for a ride, I noticed a very rough idle and white smoke from the tailpipe.

The smoke is not coolant smelling.

Also, while driving, I can feel a noticeable miss. The engine shakes at idle. The engine mounts are new.

I've narrowed it down to the #3 and #4 cylinders by cracking each fuel line loose at the injector while the engine is idling. The #3 and #4 makes little to no change in engine idle.

Things I've Checked

• Compression is 300-310 psi

• Valve lash is correct

• IP timing is correct

• Injectors are new Monarks

• Spray pattern looks good

• Swapped out injectors with known good ones, problem stays at #3 and #4cyl

My question is, could the prechambers be causing the problem? I'm not sure what else to check.

Any ideas?

Thanks in advance!