What is the cause of the problem?

Hey, my name is Dusty, and I'm one of the auto experts on RepairPal's Car Genius team. I'm here to help! Hey there! I get how frustrating it is when you think you've fixed one problem, and another one pops up. Check engine lights and diagnostic codes are like pieces of a very large puzzle. It’s also worth mentioning that codes are just a starting point, and each diagnostic scantool has limitations; if the software is obsolete or the tool isn't very sophisticated, it can limit how much of the puzzle is seen. They tell you what the car's computer has detected, but pinpointing the exact cause often requires more investigation. If your check engine light was still on and pointed to the ignition coils, that doesn't necessarily mean they need to be replaced to fix the issue. It could also have been an issue with the electrical circuit that was causing the problem; if the wire is open or short, replacing the coils and spark plugs will not help. Since your car started misfiring again and you got multiple codes, it's clear that there's a deeper issue at play, and could be due to several factors beyond the ignition coils and spark plugs. It's better to get a thorough diagnosis rather than just chasing codes, and swapping parts. This way, you can get to the root of the problem and get your Mercedes back running smoothly without the guesswork. If you have any other questions or would like help with finding a RepairPal Certified shop in your area, give us a call! 877-913-1554