So the other week I installed new spark plugs. They were Bosch YR7MPP33, I check multiple places and I was told I needed Bosch YR7MPP33. After I installed them my engine started stuttering/knocking. I checked my old spark plugs and they are Bosch Y7MPP33.
What is the difference between the two? What spark plugs are y'all running in your 08 c300?

 

MB specs call for the Y7MPP33 (without the "R") but it should not make a difference IMO. The "R" in YR7MPP33 stands for "resistor", which Bosch says is installed to eliminate interference with electronics like AM radio signals.
Are you sure all your coil packs are installed back correctly and none were damaged?


I just found this thread that has some interesting info on YR7MPP33 vs Y7MPP33 spark plugs in MB engines.
http://www.peachparts.com/shopforum/...sch-plugs.html

 

2009 C300.

Had the spark plugs replaced by local indie shop owned by an MB master mechanic. The invoice has YR 7 MPP33 as part number.

 

The mechanic at Mercedes told me they come from the manufacture with NGK

 

My owners manual in the glove box says Bosch Y 7 MPP33.

 

From personal experience, Mercedes factory plugs can be either Bosch or NGK. Had 2 cars with M112 engines. One had Bosch from the factory and the other, to my surprise, had NGK. Some engines, like the early M276, where spark plugs were developed specifically for that application with the vendor, will have only one brand available until the design is released to the aftermarket.

 

And with Direct Injection engines, I would ONLY use what is specified and install the exactly as instructed (i.e., to the precise torque specifications).

 

You have not specified what engine your car has. It makes a difference