Spark Plug Reading - Engine Running Hot?
I have a C218 CLS63 AMG S with about 31k miles. I installed new spark plugs today and based on how to old plugs look, it seems like the engine is running hot, but the car is completely stock and the cooling system seems fine, so I have no idea what would cause the overheating. I've attached some pictures. What do y'all think? Is this normal?




Regardless of mileage, these engines do run pretty hot. It's not unfathomable that you could have a failing gasket(s) causing the car to lean out a bit. Vacuum leak test and a smoke test wouldn't hurt.
Other than that, how sure are you the ecu was not tuned? I ask as I had a similar issue, buying a car that was supposedly dead stock to find out it had an ecutune from an unknown source.
Regardless of mileage, these engines do run pretty hot. It's not unfathomable that you could have a failing gasket(s) causing the car to lean out a bit. Vacuum leak test and a smoke test wouldn't hurt.
Other than that, how sure are you the ecu was not tuned? I ask as I had a similar issue, buying a car that was supposedly dead stock to find out it had an ecutune from an unknown source.




Loaded question. You can check the ecu itself to see if it happened to be marked or labeled as a potential indicator. However, now that we're not just limited to bench tuning, it's a little harder to tell without downloading the contents of the ecu and comparing to a stock cal file.
The dealership "could" but going down that road could potentially affect a warranty if that's important to you. Not all dealerships are mod friendly with some "flagging" modified/altered vehicles for any sort of warranty work short of recalls. Depends on your relationship with the dealership.
Otherwise, you'd need to reach out to a shop that offers tuning services to discuss options and willingness to check your ecu.


