Bought a 1993 300CE recently that has been maintained very well throughout the years.

After purchasing, I noticed an occasional hesitation/skip/stutter at idle while the car was in gear. Shifting to N would essentially cure it. I never experienced hesitation under acceleration.

That being said, I drove the car to breakfast on Saturday and about 2 miles down the road I noticed a loss in power. Pulling off the exit the car seemed like it was not running on all cylinders.

I towed the car to my shop and started primitive diagnostics. I determined that the coil pack nearest the firewall that sends signal to cylinders 1 and 6 was not functioning as neither cylinder was getting spark. I then swapped that coil pack with a new unit thinking it was just a bad coil pack and the problem persisted. I then plugged the original coil pack into the second bank and both plugs fired.

Therefore I have determined that I have an issue with either the DME/ECU itself or the wiring harness. I am wondering if there is a wiring diagram available that would help me determine which connectors at the DME send signal to the affected coil pack connector. I am trying to determine whether I have a bad ECU or a bad wiring harness while being as efficient as possible. For what it's worth the wiring harness looks to be in good condition physically, I do not see any corroded/rotted wires or connectors.

Thanks in advance for any help.