Hi Guys,

So after a long hard drive today, I noticed that the car will intermittently stutter at idle. The stutter is very subtle, however, definitely noticeable. It would come on every 3-10 seconds, with a small stutter, and then go away. I do not observe RPM's gauge change, but I can definitely feel/hear the stutter. This stutter only appears in comfort mode and at idle (when car is stationary, in P, N or D). Currently car is completely fine when driven hard or at high RPM's. No CEL. From my online research, it seems like this can be caused by bad engine mounts, bad spark plugs, dirty MAF, among other scary/expensive items. A little bit of background on my car:

- Car is currently at 32k km, out of warranty as of April, 2020.
- Always driven hard (copious hard accelerations, always driven in sport+ mode, numerous launch controls), but I keep up on the service. Dealer services done on schedule, as well as additional oil changes performed at indy shop between Service A/B's (~6k km oil changes).
- Fresh Service B done 300 km ago, consisting of engine oil, transmission fluid and clutch gear fluid, gauge cluster update and cabin air filter. Opted out of stock engine air filters, spark plug change and brake fluid flush (will upgrade to higher temp fluid soon).
- K&N engine air filters installed right after Service B.
- Car completely stock otherwise.

From what I've read, it seems that the oil on K&N filters can damage the MAF. Am I starting to see the beginnings of a failed MAF? Should I take the car to the dealer to ask for their diagnosis, or should I take it to an indy shop? Unfortunately not much online resource on this particular model of AMG as it is a GTS. But, hopefully you guys can help since the engine is very similar. Posted on the gts forum but again, not much activity over there. :/

Thank you in advance!

 

Being a direct injection engine, carbon buildup on the intake valves is eventually going to be something that has to be taken care of. I haven't yet looked into whether Mercedes takes this serious as a service item. BMW has long included periodic walnut blasting as part of their service. I'm assuming they still do it. This is my second direct injection engine and I expect that I'll have to do a carbon clean at some point. I've had similar stutters as you describe on my previous car and they went away after a carbon clean. Unfortunately hard driving can make carbon build up worse, because there is a temperature range at which carbon build up occurs, but you have to drive really really hard to get the temperature beyond that to start burning off the carbon. It's not easy to get the intake valves hot enough for the carbon buildup to burn up by itself, but it's easy to get it in the temperature range where it forms easier.

 

At your mileage, it's doubtful you have significant carbon build up on your valves. I did walnut blasting on my N54 335i which was notorious for carbon build up when it had around 50k miles - and it definitely needed it. The dealership covered it and the difference before and after in acceleration and partial throttle was incredible.

I've yet to hear of any M177's getting the walnut blast treatment to fix any issues - if anything, it's been sensors failing prematurely that's the issue.

 

Our cars don't use MAF sensors, so the oiled filters are likely not your issue. Try to find someone locally with a xentry to scan you car to check for stored codes that may not trigger a CEL

 

What is the difference between a regular fancy scan tool and xentry? I used a cheap scan tool (not regular fancy tool) and it showed no codes, stored nor active. Could a fancy scan tool find more codes? I’m assuming cheap < fancy < xentry?