Grau E350

I thought this was an issue in 2010 models...but.

I noticed my 2011 at a constant speed like 60 or 65 with cruise fluctuates about 200 rpm. i've never seen a tach bounce up and down constantly.

Is this an electronic issue, or has this been deemed "normal?" in the board's experience. I remember it coming up before with the 2010's.

TIA.

ImInPA

my 2011 Bluetec does not bounce around. What does your dealer say?

Live Oak

My tach is solid as a rock.

Arrie

Tach moving around can be a sign of a serious issue with the engine. I understand from your post that the engine actually runs fine at constant speed but the rev counter fluctuates, right?

If rev counter signal comes from crank shaft sensor the issue is serious as it means the engine control system would also get the defected signal. This has an effect to all engine control functions.

Grau E350

Thank you very much for the replies. I haven't discussed this with service yet, but I will. I found it incredible odd that this is occuring...I've had a lot of cars over the past 5 years (all German) and this is the first I've seen.

Yes, the tach at a constant speed fluctuates around ~200 rpm constantly. You can watch the need bouce up and down, which is pretty strange.....especially going over a flat stretch of road w/ cruise control.

ghh429

Plug in an OBD ii reader (or get the dealer) to check if it's a problem with the stepping motor on the tach or the RPM sensor (or if the engine is actually revving - you will be able to tell by the airflow).

Some cars idle like crap, some cars don't. My E55 had a bouncing tach too but had good compression and I really was never able to isolate the problem...

T100T

Was this matter resolved? I see a slight flutter on the tach when cruising, 2010 E550. No indications of engine issue.

Did you see the below under bulletins...

LI54.30-P-049068 MAR10 – 207 (coupe) up to VIN F014219 / 212 (sedan) to A079696 tachometer fluctuates by approximately 100 rpm, IC will be replaced.

thanks,

Peter

tge4

pwells is correct. There was a service bulletin released about this. Talk to your service department. There is a fix, and its instrumentation, not equipment.

marcosevo

Tge4, do you have the link to this service bulletin?