Ben'z

Hi,

My car shakes when the engine run over 4000RPM in P or N gear.
My service adviser said it is normal to keep the engine run low RPM when the gear is in P/N gear.
What do you think? Does your car do the same?

Thanks in advance for your input!

Ben

OldNate

My car does the same thing, your mechanic is correct. It is normal.

Ben'z

Thanks a lot, Nate!
I feel much more comfortable, after reading your words!

Whitey

Hi Ben, have you replaced the engine mounts yet? The car shouldn't shake a lot if the mounts are good, so maybe you should change your mechanic too

Ben'z

Hi, Dave,

The engine mount was replaced one month ago.
After it, I can still feel the shake on steer wheel when I wait for the red light.
The SA said the shaking is normal.

Three days ago, I push the gas to run the engine over 4000RPM when the car was in Parking gear, the whole car shakes. It made me feel something wrong. Then, the SA said MB has designed like it. If the engine run over 4000RPM, the gas will be cut, which cause the shake.

Ben

Whitey

Hmmm, maybe its something else then.... The thing is, how can he tell you its normal when the shakes didn't exist before? I'd suggest getting a second opinon or do a computer diagnostic for peace of mind.

Ben'z

I have never let the engine run over 4000RPM when the gear is in P.
That's why I didn't know what would happen before.

How about yours?

Whitey

Oh wait, sorry, my bad - I missed the P part! Yes, the fuel cut-off kicks in after 4000rpm causing the car to "choke", it is normal for most, if not all Benz's...sorry for the confusion hee, hee....

Ben'z

Dave,

Thanks a lot!
Now, I do feel comfortable, after two people confirmed it is normal.

Ben

lkchris

Mercedes doesn't want you to overrev your engine and therefore limits revs in neutral. This protects you from yourself.

ReZzZ320

if it weren't for this feature you'd be in deep trouble

Darkmann

I have a 01 430 and I just went out and tried to simulate your condition - in P. Now, this is a cold engine (I did allow it to idle at idle RPM) I revved gradually to 4K several times - scary noise, BTW - and no shaking at all. As I revved past 4K, I started feeling vibrations that felt like misfiring - no it didn't misfire, but the vibrations were like what you'll feel during a misfire.

BTW, why in the world did you rev up that high with no load. It's a pretty scary noise!!!!!

Musikmann

I fail to see any reason to rev your car to 4000 RPM in either Park or Neutral. Maybe it is good that you did, just to see what it would do. Under certain circumstances, the conditions that you described might indicate an underlying problem, but otherwise, why did you even do it?

Pjudd1

I agree, stop reving your car so high, and it won't shake.


-Judd

Musikmann

LMAO, you remind me of the joke where a guy goes to a doctor and tells him: When I raise my arm like this it hurts. Doctor says: Simple, don't do that.

endy

shakes? of course it shakes, it's telling you that the beast wants to come out and play

i rev it only twice over 4000 RPM on Park.. it was fun, but i doubt you're suppose to drive hard in a benz. unless it's an AMG

MB>BMW

the cut off is normal, but if u want to rev past 4000 drive the car above 10 mph and put the gear from D to N and slowy push down, u can now rev beyond 4000 rpms. Its fun to it it once in a while, but dont get used to it. Be careful.

Losiho

As others have said, it's a soft limiter, and designed to protect your transmission.

Not a good idea to rev it like that frequently......

Ben'z

Why?
I did that by accident , and it just happened and made me scary... thought something wrong with the engine.

Lancelot

In P or N when revving the engine that high you're basically putting all that horsepower on the distribution chains. NOT a good idea...

Ben'z

Thanks for all the reply!
It was a stupid accident.
Of course, I will never do that again!

lxl_Jeffro_lxl

I do it to show off, but it's a poor choice on my behalf....

Lancelot

I noticed you drive a Diesel too. Here in the Netherlands during the mandatory annual road/safety/emmisions test, they FULLY rev up Diesel engines UNLOADED!!! to measure sooth output. There is a lot of debate on this since on some cars the distribution failed thus destroying the entire engine. They should dyno the car and then measure it...

lxl_Jeffro_lxl

I would be scared to redline my RPM gauge in park or neutral.......That sounds crazy though! I want to dyno my car by a professional, and see how he goes about doing it. If he screws it up, it won't be my fault. ha

softbenz

My 2 cents:

Achieving 5000-6000 RPMs under Loaded vs. Parked engine is not the same. Over-reving limiter saves your engine (read valves, pistons, rings etc) from harmful exertion forces imposed on the engine when it is reaching that many RPMs in second or two. I thanked MB for making it me proofed