gregjc

I have started getting an intermittent misfire. After maybe 20-30 minutes normal driving (running perfectly) I get a misfire, drop in power, rough idle. Had it 3 times now. I've pulled over and shut down for perhaps 30 seconds, restarted and it runs perfectly again. I have pulled codes 0300, 0302, 0352. 0352 being misfire cyl 2, open circuit control wire to coil. I tried swapping No.2 coil to another cyl to see if the misfire follows - but of course it then started up and ran perfectly! Will try again next weekend and extend this investigation - but it got me to thinking of replacing the engine wiring harness - but can't find anywhere that sells new ones. Has anyone done so and found a source? Suggestions on that and the misfire would be great, thanks. BTW I have recently replaced inlet manifold, cam solenoids and battery. When not throwing the 352, there are no other DTC's.

Rudeney

If it's running good with no error, you might have just had a loose/dirty connection to the coil. Try some contact cleaner there and keep running until it throws another error (or, maybe it's fixed now).

Fatz

I found the wiring harness for the 550 (A 273 150 13 33) at https://www.genuinemercedesparts.com/ last year. I don't know if that link is good but the MB location is Robbinsville, NJ.

gregjc

Fatz, thanks for the link. Unfortunately they don't ship overseas and I'm in Australia. If anyone knows of another source I'd be grateful. Thanks Rodney, will try some further contact cleaning and diagnosis this weekend, too.

gregjc

Just to close this out for others that it may help. I eventually tracked this to a faulty coil. Replaced them all and all running well after about 500klms. I learned during the exercise that I had made a mistake as a novice user of the Icarsoft 980 : I used "automatic diagnose" and it for some reason (despite me correctly choosing my 350 engine) the scanner thought I had an 8 cylinder engine and pointed me to cylinders 5 and 6 for the misfire. When I eventually) chose "manual diagnose" I got the correct clue to cylinder 1 misfire - and was able to track the faulty coil. Hope this helps someone at some time!