[username604]

Last week, my 335i had the service engine soon light come on and the engine was shaking, and so i restarted the car and all was well. I've also had a bit of a rough idle lately, and so today i dropped the car off at the dealer.
My service adviser mentioned that there would be a $140 charge if the problem was not covered under CPO, but that it probably is since it is engine-related.

My car has 47,000 miles and I have yet to change the spark plugs.
Am I going to get charged the 140 diagnostic fee to be told that i need new spark plugs?

In retrospect, i should have just changed the plugs myself with that $140 (plugs and the proper tools which i don't currently own).