On my '74, 240D (automatic), sometimes at an idle, I think it drops a cylinder. It doesn't use or leak any oil, and it's just momentary - actually, it seems to be getting better the more I drive it, as it had previously sat for awhile. Currently, it's in the shop for a valve adjustment, so I'm not sure if that will help or not. There is no loss of power when I take off, and performs wonderfully (for an old 240D) when taking hills, or driving down the highway. What would cause this? Also, it does seem to belch out darkish smoke when I let off the accelerator driving down the highway when slowing down quickly. Again, runs fine when driving - only idle issues. Thoughts, anyone?