Today I just noticed when my car was in neutral I revved the motor it wouldn't turn more than 4,000 rpms. Even when I put the pedal to the floor it would not go over 4,000 and the motor sounded very weak like only half of the cylinders were firing. I then took it out for a ride and it seemed to accelerate ok and would pull to redline when asked to. However, I also thought I heard some pinging a few times when car was at high rpms. I'm not sure whats going on here. I'm wondering if anyone can give me an idea of what the problem might be.
I've also recently noticed that the car sounds really weird when its not fully warmed up and you get on the gas. It almost feels like there is a vibration from the motor or exhaust which is louder than normal and very noticeable. This goes away once the bar is fully warmed up. I've never experienced this in the past. The car has 25,000 miles on it. Any advice would be appreciated.

All the M156's wont rev past 4k rpm at idle, unless you took off the rev limiter with a tune.
These engines are known to make odd noises and slight vibrations from time to time but nothing to get alarmed about unless its very noticeable.
Noticeable vibrations can be caused by worn motor mounts (an easy fix).
Pinging might be caused by bad gas.

How long has this been going on for?

you have a stock exhaust system ?


Also when my old car sat for a while it would make some funky sounds until it warmed up . Most noticable a whine that sounded like a TQ converter and also some loud ticking .

Yes the car is completely stock with the stock exhaust. The funky sound when cold could be a drive train noise possibly. Its more of a vibration than a ticking noise. The car just feels louder and rougher as it accelerates. This just started about a week or two ago.

I never noticed that the car didn't rev past 4,000 in park but I'm sure this has been the case. Its just that when I pushed the accelerator down in park the motor sounds like ****. Once it hits about 2,000rpm the exhaust note is way quiet and feels like only half the cylinders are firing. I have I think service D in 30 days according to the cars onboard computer.

My 215 CL65 won't rev past 3000rpm in neutral either.

R.K.

I've been trying to better understand whats going on so I can tell the dealer when it goes if for service next week. What I've found is the when the car is not fully warmed up and you accelerate hard there is a knocking sound coming from the rear of the car (feels like the right side) when the rpms get above 4,000rpm. Under mild acceleration I do not hear it. Once the car is up to operating temperature I don't heard it either. Could something going on in the differential that stops once the fluids in the rear end have reached operating temperature. I can't understand what else it could be. Any ideas?

This sound is normal most AMG/// engines

How come I never heard it in the first 20,000 miles and now it's apparent.

Make a video.

let us know what the dealer says.

Put a bottle of chevron in the tank and go for a spirited drive.

The 55 and 63 n/a motors are very vocal with lots of clicketyclack by default. However, if not driven hard they will build up carbon deposits and sound and feel very rough when cold.

If the chevron helps, change gas brand. Sunoco is the worst in my region.

as far as additives for real bad carbon build up i've heard sea foam is good.

on a bike- sure vote with both hands for it.

chevron-techron is the only approved by mb additive and does work.

why risk anything else?

Seafoam can be added to the oil or the gas tank. I heard that it causes alot of smoking from the exhaust when added to the oil. I Seafoamed my M5 (via the gas tank) and it did help with carbon build up for a while. The E39 M5 has a design flaw that can cause excessive carbon build up that is so significant the engine has to be torn down and cleaned...Thank God for warranties!

Tried to make a video but you cannot hear the sound well enough. Car is going in for service next week. I just hope this is not a sign of the camshaft lifter problem for which the class action suit exists.

I treated a whole tank of gas with the Chevron Techron and the car is running much smoother. Seems like the noises I was hearing are less but I was unable to really test it out. I will see when I take it home tonite when the motor is not so hot.

So I took the car into the dealer for the knocking. I was told that it was one of the rear shocks which was replaced under warranty. Got the car back and it's still making the sound and again only when the car is not fully warmed up. Today the noise was particularly load and my check engine light came on. I'm bringing it in the road test with the mechanic.

Brought the car back to the dealer who replaced the engine and trans mounts. problem solved

Good to hear it wasn't the engine!

Glad to see everything got taken care of.

so the techron solved your problem, but the engine/tranny mounts helped isolate the noisy motor from transferring its clatter to the body and you hearing it

on a related thought- interesting. i thought the hydraulic bushings collapse early only on the v12 motors... good to know that the n/a motors are not safe either.