[surf2727]

So I've got a '10 335i w/ 49k miles on it and have been getting a consistent misfire in cylinder 1 and notice rougher startups than in the past. I changed all spark plugs earlier this year and also swapped coils to check if it was them that were bad...nothing. I even replaced the coils. Anyways, I know I could be wrong, but I've attributed all of this to carbon buildup within the manifold (or bad injector) and was curious if (and how) people brought their cars in to the dealerships to get them to perform walnut blasting? If under warranty, was it free? What did you say when you brought it in and how did they diagnose it? Any other feedback would be great as I will likely schedule an appointment soon. Oh, and my car is currently covered by BMW's maintenance plan for just one more month, but my warranty is valid for another couple of years. Thanks for the input!

Lastly, are injectors covered under the maintenance plan or warranty?

[guanyum5]

Hey bud. I'm in a similar situation. Have an 08 e92 335i with 62000 miles on it. Took it in for service this past week due to a washer fluid pump leak. Also mentioned that ever since I got the car couple weeks ago, I noticed cold start idle was a bit rough, and was guessing it was due to carbon buildup around the intake valves. Sure enough, the dealer said it was. I asked if this is covered under CPO warranty, and my SA said it is not because it doesn't involve any "defective parts". I also have the extended maintenance package, which doesn't apply here either. She said its attributed to "poor quality gas", and asked me what kind of gas I use. I said I've only pumped 93 from big vendors like shell, bp, etc. Who knows what the previous owner did. They did go ahead and clean them out for me since it could only get worse and said engine runs very very smooth now. Picking her up today and have to pay the $50 deductible for now. The tech who walnut blasted took pictures/documented the process. My SA said she submitted some paperwork with the pictures to see what BMWUSA can do for me, since I literally just bought the car, and am not technically at fault. Worst case, I'll have to pay $400 out of pocket for the service. I have read some threads on here of people having it covered under warranty because they had some other related parts malfunctioning such as coils/injectors, so it was tied in along with that. Good luck.

[Artmasterx]

Wow, you only had to pay $400 for walnut blasting AT THE DEALER. Up hear they are charging more like $750, and even independents are charging $4-600.

I need to move back to NC. NC State FTW (except this football season...)

[guanyum5]

So just an update: The car feels a bit smoother for sure (though I'm not sure if its placebo), but unfortunately I'm still getting idle shakes in the engine similar in degree to before service was done. It may be a toned down but its def still there. Am I supposed to be getting these bumps at 62000 miles? They are random but happen every 2-3 seconds, sometimes 2-3 bumps in quick succession, sometimes a more prominent single bump. This is happening regardless of engine/oil temp, at cold start and at a stop light when engine is warmed up. Could it be a coil/injector/spark plug on its way out? I'm just trying to figure out if this is something I should be worried about or if its normal. I will keep an eye on it and see if it gets any worse. Anyone been in a similar situation? Thanks.