skipwalton350

About 8 months ago I got a misfire on our 06 ML350, that went away after we stopped for a couple of hours. A month or so ago it came back for about 10 miles with a cyl 1 misfire. Last week it hit hard and did not go away. I put my scanner on it and the only code that came up was the 301 cylinder one misfire. I got a new ignition coil, put it on and it was better, but still had a miss. Code came back on. I should have swapped coils to see if the problem followed, but decided that it would not. I took my car to my INDY shop that I trust 100% explained the problem and what I had done, and suggested that maybe the plugs were shot since I had no idea how long they had deen in the motor. Number 1 plug had a collapsed tip where the electrode was shorted out. All plugs replaced, throttle body cleaned out and now everything is fine. Scope showed nothing in the cylinder itself. Not sure why a shot plug worked for that long then went dead, but it may be something to put in the back of your mind next time you have a miss. Old plugs were Bosche, new plugs are NGK.

Plutoe

Another positive take is don't wait for months for a problem to reappear and two don't waste time and money on parts that are not required----properly diagnose the car---if you can't find someone who can!

skipwalton350

UPDATE: Today I got the misfire again, same cylinder, but when I restart the engine, misfire is gone and CEL goes out. All plugs were replaced along with the coil pack for that cylinder. The misfire hit under moderate to hard acceleration. Only code that came up was for the #1 cylinder misfire, no other codes came up. I use the iCarSoft scanner / reader. I'm going to have my INDY shop pull that #1 plug and inspect it. Anyone have this happen to them?

skylinrcr01

I had that happen on my old Audi, turned out to be a bad injector. I'd try that next, cheapish to replace too.