I am planning on getting this car to a shop ASAP, but wanting to check on one thing first.

I have a 1993 Mercedes 400SEL (W140 4.2L) that will start and run perfect when the engine is cold. However once the engine is fully warmed up and you turn the car off... when you restart it is either hard to start or when it does start it runs very poorly... it will misfire, splutter and barely run. This has been going on for awhile and has slowly gotten worse and worse. I finally had parked the car, but will start it and run it occasionally. The car has fairly new distributor cap/rotor button, etc. I also have already swapped out the old EZL with a good used one and the problem persists. The car also already has a new engine wiring harness (about 4 years old).

My normal MB mechanic can't look at the car until April 2 and I cannot wait that long. I do have another mechanic/shop lined up, but wanting to see if it is something I can troubleshoot myself. Someone told me it sounds like the ignition coil may be going bad, but I do not want to start throwing costly parts at it. An ignition coil for this car is over $100, so I do not want to replace that unless I know that is what the issue is. I let it start and run yesterday... it ran perfectly, smooth as silk. I let the engine warm to full operating temperature, shut it off. I restarted about 10 minutes later and it was missing, sputtering, etc. It was like it was literally running on 4-cylinders when I would put it in gear and it would try to stall out and eventually the exhaust started smelling like rotten eggs.

My check engine light does not work, no not sure if it would be on or not. Someone said there is a way to check for codes by a light/button under the hood and I have tried that before, but forgot how to do that and do not know how to read the codes.

Any help appreciated.

* I was also told it could be the 'output shaft sensor', but not sure how you check it or replace it?? Would that cause poor running on hot start-up?