I may be experiencing a similar problem with a 94 E420. It started hesitating while driving at highway speeds; and idle would hunt up and down. Computer indicated a fuel injection or open circuit fault. MB tested fuel injection and said it was OK; they then wanted to replace the wiring harness (approx $1300; 7 hours labor @ $100). An independent shop thought the harness was in good shape and replaced plugs, dist caps and rotors. It seemed to run better but continues to record same code immediately at ignition after reset and idles slightly rough at certain times.

Car has 90,000 miles. Has anyone seen this problem; does the E420 have the same throttle actuator?