I'm having a real problem with my daughter's '87 300E. The fact that she is 19 and not car savvy doesn't help troubleshooting here!

The car will run fine, but occasionally will experience a "bog" where the car doesn't want to respond to the gas, and sometimes stall. In my driving, it only happened once to me in heavy traffic, but it was only momentary.

The other day, while driving it again, it happened while turning into the drive. Pressing the gas, it would bog. Playing with it, if you could get the RPM's up, it would catch. At idle, the vacuum (economy) gage is normally high. When this happened, the gage was considerably further towards the red, about 1/3 over. Pressing the gas part way, it would go all the way into the red. I also smelled gas. Then I noticed black smoke (over rich!) coming from the exhaust.

This condition is intermittent, making troubleshooting very difficult. It will clear up just as mysteriously as it happened.

Other notes: Plugs, wires, cap & rotor are all good. O2 sensor was just replaced, as was fuel filter (both were on hand and due).

I've spent hours searching here and reading threads without hitting that majic "BINGO!!", that's the problem.

Any insight, solutions, tips or pointers to likely items would be greatly appreciated at this point.