Background:

1993 500SEL // 200K miles // Excellent Condition

I purchased this car in June from the original owner. He purchased it from the local dealer and it was serviced at the dealer for the entire life of the car. It never missed a service until the 180K service, when he was getting rather old and didn't drive it much. It's now at 200K and will be getting those services soon.

Not long after I bought the car, the water pump began weeping. It took me a few weeks to get the time to replace it, and in the meantime I kept distilled water in the trunk and topped it off as necessary. A few weeks ago, I opened the expansion cap to top it off without realizing that the water level was higher than I anticipated, so water started spouting on the engine. After a few moments, I threw a towel over the expansion tank to prevent more water from dousing the engine. The car was not running when this happened and it was straight water at this point.

When I started the car to drive it later that day, it ran very rough and I assumed I'd gotten the cap or plugs wet. After several days of trying to dry everything and blowing everything off, it still would not drive normally.

Symptoms:

The engine is only firing on four cylinders. When I put the transmission in D, it stalls after just a moment. If I put the transmission in reverse or first, it will drive. When I manually shift from first to third, it will stall through second, but then shifts to third and then fourth without issue. I learned this by trying to drive it to dry the engine, initially.

Steps Taken to Cure:

I replaced the following items

• Water Pump
• Both caps and rotors (Beru)
• Spark plugs (Bosch)
• Right coil (Bosch)
• Crank Position Sensor

I have read about 40 hours worth of posts everywhere using every search term conceivable and have yet to fully comprehend what could possibly have cause the issue and what the issue is. I have disconnected power to the injectors for the non-firing cylinders while troubleshooting.

I suspect the EZL/ICM, but no water even reached that side of the engine. Of course, I am assuming the water on the engine caused the issue, but that may be a false cause. This engine ran perfectly prior to water spilling onto the engine.

Any ideas or further insight? I do have an appointment in a couple days with a semi-retired Mercedes mechanic who came up with these cars. There is a wonderful local indy shop that I trust, but they're a few weeks out and this mechanic came highly recommended from another Mercedes owner.

Thanks for reading the essay I've written as my first post.

John