nickm

Hi all,

I just picked up a fully loaded C350 after my CLK 430 died when a guy blew a red light.

Love the car, only one thing:
I noticed that the RPM needle is not exactly still when you're driving. If you look at it, it actually moves a little bit, up and down, nothing tremendous or exaggerated, but if you notice you can see it. Does this happen to anybody else? Thanks

hadjionm

My C220 CDi diesel did the same thing. When at idle the needle moved about between 720 to 760 revs. It stopped doing it after about 3 months. It is now dead steady.

BSully88

Ive noticed this as well. Very minor jumps with the needle but haven't thought much about it...

hellasmania219

hallo,

i have this same issue on my 2009 c300 4-matic sport 6000 miles.

check my video RPM issue video

the fluctuation occurs in the below cases:

Park, drive, and reverse with brake applied.
Neutral: brake on and off
A/C: on and off
Aftermarket HID: on and off

In all the above cases the RPM pulses. it seems to come in waves as some moments the car runs perfect and needle idles at a stand still.

the fluctuation is upwards and can be a whole tick mark on the tachometer. last night it jumped almost two tick marks and the car sounded and felt like it was revving.

the pulsing occurs almost anytime you look, but feeling and hearing is hard if at all possible to do most of the time.

the needle has been flickering like that since i got the car but i didn't notice until after owning it for a week...up until recently i never felt or heard but not i can pick up that the engine is actually spinning up when i focus

charliele729

I also have this issue, i notice it when I am cruising on the highway, I took it to the dealer and they said they have email MBUSA because the foreman did not no what it was. I drives like normal, and it is very minor, I will let you guys know when I get an update.

jctevere

I have jsut noticed that mine does this too. But it has never done it before. I just hit 20,000 miles and did my second oil change. I also topped off coolant and put in a bottle of techron fuel cleaner to a full tank.

Nothing was botched in the oil change, I have done tons. I did add coolant from a different spec (325.0 instead of 325.3) It was such a small amount and I added a bit of bottled water. Perhaps I got air into the cooling system?

And I highly doubt that it was the fuel cleaner bottle in the tank, or any of the above for that matter. Because after I did everyhting I let the car run for about 20 minutes and did a bunch of errands and driving, no issues. Then I went home, let the car sit about 2 hours and did a 20 minute highway run. During this highway run I was going on an uphill incline with cruise control on and with my x-pipe I heard almost what I would describe to be my car hitting a top speed or rpm limiter.

I look at the tachometer and see the needle jumping about 1/2 a bar to as much as a bar in either direction. The car runs fine and everything. I am wondering if I have just never noticed it before, or if it is the cold weather. Over the past month my car's rpm needle started to jump on idle during cold starts, but I never had it move when driving, but now it does.

On another note, I just remembered that before I let teh car rest for 2 hours I just did a TCU reset. (key to on position, hold down gas pedal, key off, let go gas pedal). Perhaps the TCU reset to an earlier firmware or something and the ECU and firmware on TCU don't match? I am going to go by the dealer, but I am afraid that they will blame the oil change, coolant top-off, aftermarket HID, or fuel cleaner and deny warranty???

Any suggestions?

EDIT: I also wanted to mention that it isn't 100% of the time, and while when idle is worse when cold, the rpm jumping while driving is worse when the car is fully warmed up. And it seems to be worse under certain conditions. Not really noticeable on cruise control, but more noticeable when I drive the car (even if I provide a constant speed or a steady foot). The problem gets worse when there is a higher load on the engine (not neccessarily higher rpm) but when there is a hill or an incline.

hellasmania219

my 2009 w204 did this at idle all the time. I am at 28000 miles now and don't see the issue as much. I had a transmission/computer upgrade and such done at dealer maybe these helped?

tanktube67

It’s totally normal.

Ron Jr

This is normal, I've had this on every car that has a tach.

kowyzg0moo

If you have a German automatic, it will always fluctuate. Because you're seeing the ECU trying to adjust to the conditions that are on the road, as it's constantly thinking.

It's like this on my old BMW 328i, my C300 and now my C350 and even on my folks' E550. This is especially true when you hit the brakes on idle. You'll see the RPM dip - just like how you'll see the ECU dip your RPM down as you brake; it's all in the fun of owning an Automatic car.

Now if you have a manual and it's doing that...that might be another story.

jctevere

I wouldn't be so stubborn about this if I have never head this before at all. Also, my father's sl500 nor my sisters 2011 w204 have this rpm needle fluctuations. I am going to bring it to the dealer next week and see what they do. If the problem remains I will just have them note it, and if my ECU fails out of warranty I will say that it was like that during warranty and they never replaced it. Lol.

noka

Haven't noticed on my '09 C300 4Matic with 10.5K mi.

RLE

Steady as a rock, in or out of gear, in my '08 C300.

B300AVA

Sorry for jacking an old thread,
But did anyone know what the solution is?
Im having the same issue. Floppy rpm needle.
Car is a brand new 2013 c300 with 300km on the clock.

zero0809

This happens when I play my ipod, but when I turn it off, it becomes steady. I dont know if I should continue playing my ipod now. Anyone have any suggestions?

toni.cerkez

Hi,

I have similar issue:

What could be problem?

Skyline45

It's not a problem. All cars that have a tach have done this in my experience. Granted, the only cars I've had before my W204 have been older vehicles that have analog tachs.

pedle

Same problem on my 2009 C320CDI (with 7G tronic) - when I am driving steady speed RPM needle is slightly oscillating up and down and I am really upset about this. It is definitely a problem because on my fathers 2009 E350 CDI (7G tronic) and my sisters 2010 GLK220 CDI (7G tronic) RPM needle is steady all the time. In Mercedes service they already updated my engine and transmission software - still the same. Pleaaaaase do you have any new info what it can be??????

charliele729

My ols 09 C300. One of the tech found out it was a wire ecu issue, it been a long time time but I do remember it was an issue w the ecu wiring being mixed up or loose. Have you tech take a look at that. It took care of all rpm fluctuations for me

Jhaley

I was told it was normal. 25-50 rpm fluctations at all speeds including idle.
saw another post with same issue. Someone suggested replacing the o ring on the top of the dipstick. I was was rock hard, even broke apart upon removal.
After replacing it needle is rock solid. 2 bucks from Mercedes. Problem solved. Hope that helps.

W204 Benz

Hey guys it’s my first time writing a couple of months ago I realized that my rpm was fluctuating up and down and the car seemed to be shaking a bit. Brought it to the garage and no one could see the problem. Recently a check engine came out p0302 cylinder 2 misfire. The sparks plugs and coil all have been changed and the fuel injector was changed as well. I went to Benz and they could not diagnose the problem. They wanted to open the engine up to “explore” which would have been 3000$ just for labour. So I said yaaa no. The misfire stops after 2000 rpm’s. I’ve recently bright to to a euro dealer and they told me I need a new engine, while another mechanic said it’s impossible that you need a new engine. They performed compression tests in the cylinder which came to 198 psi. (Mercedes) the car is a 2013 c 300 with 86000 km on it. Won’t be spending crazy money to put a new engine inside if it’s something else. Anyone got any ideas? Seems like no garage can solve this problem…

BlackML550

You might be better off starting a new thread and link this one in your initial post to get a better response. Long, old threads wear people down and limit the response rate. The problem you have could be so many things and that's why is proving hard to diagnose.

Be clear about age, service history, codes, work recently done, and symptoms. Good luck.