The Lover

Hey Fellas

I got this problem with my W204 2009


Look at the rpm when I break the rpm goes up alone while it suppose to down with the speed odometer
any solutions ??

dolvio

ummm lol... Your car is downshifting so revs will bump...

Carlos.33193

Perfectly normal, your car is automatic so it's downshifting through the gears, the gear ratios change as the car downshifts so the engine RPM has to go up to match it.

It's the opposite when you are accelerating, the engine RPM drops as the car upshifts.

The Lover

But sometimes it will do this alone in Park mode ,and the gear ratio RPM goes up and down like I am accelerating for 1 - 2 seconds , you think this is NORMAL
I own this car for 4 years so I already knows the normal things

dolvio

Rpms will bounce around for lots of reasons. Activate power steering pump. Aircon. Etc.

aamirani

Sounds and looks normal to me

The Lover

now it drive me crazy , sometimes when i am stopped , the rpm goes vooov like iam preparing for a race, stupid isn't it !
by the way , I installed on my car some modified parts , like x-pipe , AMG exhaust system
and recently changed the ac compressor
thanks for the replies guys but any other solution ?

victort

something's definitely wrong! take it to the dealership immediately for a thorough inspection

Acapulco Bill

Could be many things: Injector stuck open, MAF misreading, bad signal from an 02 sensor, leak in the intake system, problem with the crankshaft sensor. The computer should throw a code which a MB dealership or a highly qualified shop can diagnose. Best of luck.

The Lover

if I took it to the stealer , they will rip me off even if it's small as a ring
that's why I came to my family here asking for help
if none make sense after I would take it and cry

The Lover

the stupid Xentry shows all clear , nothing there , so it's mechanical can't be figured by OBD2

Acapulco Bill

The M272 3.0L engine has a variable length intake manifold, however this would only affect the intake running the engine under speed, not a runaway idle. Even if it is a sensor, this may not always throw a code. Complicated.

As for MB dealers, my closest one is nearly three hours away. Worth every minute of the drive however, the service a Stuttgart Motors Cuernavaca is fantastic with fair prices for their excellent service. Maybe there is a better MB service department in your area, if you can you should check

The Lover

Acapulco Bill , You mentioned the Mainfold Intank , this part goes above the engine , I have changed this one last couple of months with an OEM Mercedes Part , and As I tell you it won't give a code , so I have no way to figure it by Xentry , and the closest dealer is only 10 minutes driving , but will cost muuuuuuch as u know , and already did a complete service , even spark plugs and cleaned the air sensor gate
but do you think this is caused by the Xpipe I installed ??
Any chances

Acapulco Bill

"...cleaned the air sensor gate...", just got another GM car back from the shop with this problem, the engine would rev at about 2000 RPM, making driving the car unsafe. Perhaps the cleaning caused the problem or didnt fix it. I would suspect this first, the MB dealer should check and/or fix this for free if this service was listed on your bill.

It is rare but perhaps one of the pre or post cat 02 sensors became intermittent with the Xpipe install. This would not throw a code, just output bad data to the ECU. Had this problem on my exotic V12 after installing Magnaflows.

Unfortunately if the 02 sensor causes excessive fuel input, this can cause excess hydrocarbons to go through the exhaust to the cat, and an 02 sensor failure can result.

So take care of this irregularity ASAP, whatever the source.