Hi,
I've got a strange problem with my W140. Straight six engine.
After cruising for more than an hour, on german autobahns, at 85mph+, I was suddenly forced to slow for bunched traffic. The engine misfired, would not pull at all. Stopped at the next park place and turned off the engine. After five seconds turned it on again and everything was clear. This happened twice more during that week. I wondered if it might be due to cold air, -10C, but I guess not.
Later on that trip a similar thing happened outside Madrid, but this time the air temperature was 22C, so its not a temperature related thing.
When I returned home I got the local M-B dealer to check what was stored in the computer. They tell me that it showed misfires on cylinders 1, 2 3 and 4. They had no idea what had caused my problem, and said that they had contacted M-B (UK) who had never heard of anything like it, as it was intermittent, and had no suggestion to make.
I have lost confidence in the car for high speed touring and would welcome any suggestion of a fix

The USA requires a monitoring system called ODB2 that watches all of the other computers for that type of problem.

The most common failure that causes misfires & then goes away & comes back at times is a defective air-mass sensor.

Good luck with your problem.

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Thanks M-B Doc,

In it's life with me, three years, the 320 has gone thru two of those. is that normal, or has there been a bad batch, or might I have a connection problem in that arae?

thanks again.

Seen this problem quite a few times. It is in the Ignition coil pack's wiring harness. Remove Black plastic cover over Valve cover to gain access to the Coil Pack's. You will probally need to remove the air intake pipe & reinstall it. With the engine running wiggle & move the fat foamed insullation of the wires leading to the coil pack's (don't worry) You won't get shocked. Doing this will probablly mimic the problem. Sollution Repair damaged wiring for coil pack's by replacing harness or have it rewired by a skilled tech.
Good Luck !