ClasseMiaMadra

The car will start to stutter while driving on the highway. Thought it was related to O2 sensor (had code P2656) but that was not the case. Thought would go away after service but didnt either. I think there is a correlation with rain or wet, humid weather but not sure. When this happens it revs up and down when on idle. Shifting gears or driving style will not change anything. It goes away same as it comes, randomly on its own after few minutes. However the last time this happened I paddle shifted to 3rd and then when accelerated it was not there. The car is at 94k miles and in good condition otherwise, no codes, CEL etc.
Thoughts or ideas are appreciated.
Thx

muleears

Have you had the codes read recently? After the O2 fix?

ClasseMiaMadra

I have not but this happened before and after the O2 sensor change. Also there is no CEL on. Can there be codes w/o the CEL on?

Thx

muleears

Yes, there can be codes that are "pending" and haven't tripped the CEL yet. I'd get them read. Most Advance Auto and Auto Shack type places will do it for free. I'm sure someone who knows more than me will chime in eventually.

ClasseMiaMadra

So I got myself the Mercedes-specific iCar code reader and sit showed all clear. So still no codes, no lights but the problem keeps happening and with increasing frequency. I figured out that I can down shift it hard and make the problem go away but this of course is neither practical nor an actual solution. I'm now thinking that this is caused by regularly replaceable parts, starting with the spark plugs and /or coils. Any feedback or thoughts to share?