The Lover

Hey guys

I don't know where to start from , but I changed the spark plugs 3 days ago , on 80k miles I used
Denso (3442) FXE22HR-11 Iridium Long Life Spark Plug

, and today it gave me the check engine light , when i plugged the OBD2 scanner ( not xentry ) it returns these codes

P2541
P0300
P0301
P0302
P0303
P0305
P0171

And when I change the gear from P to D , it chunk , make me feel the car wants to turn off , cuts for 5-7 seconds then start to feel the car is heavier and slower .

P.S : I am going to take the car for diagnosis but want to hear some advices from my beloved members of MBWORLD first

Thank you guys and sorry for my bad English

jvanbrecht

First, wrong forum, you want the C-Class W204.

Secondly.. something is seriously messed up. for the fun of it, I pulled up the trouble codes.

P2541 The fuel pressure sensor of the low pressure circuit has a short circuit to ground.

P0300 Misfiring
p0301 Misfiring of cylinder 1
p0302 Misfiring of cylinder 2
p0303 Misfiring of cylinder 3
p0305 Misfiring of cylinder 5

And I have no clue what P0171 is..

Did you use the right plugs, did you torque them down to spec. Do not run your car as you will cause major damage till you fix it.

abcut973

How did you change your spark plugs?
P2541 is the low fuel pressure error code
All the P0300 to 305 are the misfiring error code for the respective cylinders.
P0171 is saying your bank 1 is running lean. Too much air, not enough fuel. This one is related to the low fuel pressure code obviously.

The Lover

I changed it in a car shop , waited for the car to cool down , and they changed the spark plugs by removing the old ones and installing the new ones obviously , or maybe there's a special way to change them , if there please let me know

And what you guess that cause low fuel pressure error code ?

Also the P0300 codes appeared before I changed the spark plugs , so I thought after Xentry scan I need to replace them on 80k miles , and now reappeared again !!

abcut973

So looks like your original misfiring problem was not caused by the spark plugs.
The low fuel pressure could be caused by a faulty fuel rail pressure sensor or a faulty fuel pump. Why is this showing up now i don't know .
Your next step would be to replace that part and see. Check the fuel injectors as well.
If your engine still misfires then it might be more severe with probably low compression in the cylinders.

Ingenieur

this is a V6 correct?
and 4 cylinders are msifiring (probably all are?)
so both banks are affected
lean and low fuel pressure
check the fuel pump/pressure

The Lover

This is a V8 AMG M156 engine

The Lover

Hey guys

I have done a scan by Xentry

And tested some components ( Fuel Pressure Sensor ) B4/15
And the volt from the Fuel sensor is 4.85 Volt that I checked by a Voltage device, so I guess it's Ok but it shows on Xentry 3.51 bar , and the engine speed is not Ok I guess ,

these are the pictures friends , sorry I'm dizzy trying to figure the issue because I'm not taking it to a dealer to rip off , only if I'm done not figuring the issue then stealer will be the last option !!

Merc63

Did you check gap on the plugs?

Confirmed they are the correct plugs?

The lean code could be from the back of the air box not sealed properly when it was removed to change plugs.

Confirm fuel pressure. Confirm fuel pressure sensor is not faulty.

I'd try different plugs.

Tranny is clunking because engine is not running good.

The Lover

I confirmed they are the correct plugs by denso website also I provided the plugs number above
I dont know if its the fuel pressure or fuel pressure sensor that causing the problem ,i uploaded the xentry resault for fuel pressure and sensor above
Do you think the battary will caus this ?
Regards

mthis

Have u checked out 02 sensors?

The Lover

I have checked them by Xentry and it says Ok , I will reinstall the mas sensor and the gaps again to verify
But you think the battary will cause this because im still using the factory battary til now 80k miles

Ingenieur

the fuel pressure is a little low (3.5 actual vs 4.6 bar spec, ~50 vs 68 psi)
is it supposed to be checked with rpm's > 1500 and < 70% load ?
pretty sure it's regulated by a vaccum diaphram

the 647 is idle speed

if the fuel pressure is low that would account for misfires, the lean condition and the low sensor reading

could be:
fuel pump (doubt it since it's making pressure)
bad regulator (not closing the return down to increase rail pressure)
fouled fuel filter (I assume these cars have one)

after looking at some parts diagrams it looks like the pump controls pressure?
could not find a filter, regulator or return/by-pass line?

VividRacing

I bet there's a vacuum leak after the MAF sensors causing the system to take in extra air after it's been metered. Probably something wasn't put back together after the spark plug install or something got broken. The missfire codes could be caused by this issue, this is a long shot at hoping it's something easy to fix haha

Actually after reading the codes again P2541 seems like the one to go after first. Check to see if any wires look damaged!

The Lover

Sorry for not understanding you correctly , but what you think is the problem
Should I check the pump control pressure or fuel filter , pherhaps the fuel pump it self , im lost
And thank you for your help

Merc63

The filter is on the pump and the system doesn't return to the tank, it dead heads to the fuel rails.

Get new spark plugs. Check the gap before installing.

VividRacing

Maybe the fuel pump itself is internally shorted to ground, so many possibilities! If anyone has the fuel system wiring diagram I wouldn't mind taking a look at it

The Lover

I will recheck the MAF sensor locks and will drive for a day to check
But when I try to go on from 0 to high speed it doesnt accelerate immediately , it doesnt respond on time to go fast so there is 2 seconds the car is heavy to accelerate

Sorry for my bad English and thanks for helping me

VividRacing

That hesitation you're feeling is the missfire, check the spark plug gaps and part numbers. Once you're sure that is okay start looking into the fuel system

The Lover

The spark plugs are new. And made by Denso 3442 I mentioned it above , specified for c63

I rechecked the gaps ( black rubber that close on the spark plugs )
But what I dont understand is why its not accelerating immediately from 0 -100 , it takes seconds to feel the engine responds to accelerate

Thanks again

Ingenieur

check fuel pressure at >1500 rpm
if it meets spec 4.6 bar, it's most likely not the pump, filter or pressure control

the misfure was occuring before the plugs were replaced
I can't see plugs causing the low fuel pressure/lean faults
some sites list that plug as OE equivilent to the NGK

your sensor is reading so perhaps the pressure IS actually low?
low pressure = reduced fuel delivery rate = lean condition
this would account for the pressure and lean errors

as someone mentioned:
check all the stuff that was removed to do the plugs, especially for air leaks

quoted from diagnostic sites:
"Lean misfire" can occur when the air/fuel mixture is too lean (not enough gasoline in the mixture) to burn. This can be caused by a dirty, clogged or inoperative fuel injector; air leaks; or low fuel pressure because of a weak pump, restricted filter or leaky pressure regulator. Low fuel pressure would affect all cylinders rather than an individual cylinder, as would most air leaks. A leaky EGR valve can also have the same effect as an air leak.

Another common cause would be a fuel delivery issue causing the engine to misfire causing a P0300 code (or any misfire related code) to be stored in the computer. It can be a lack of fuel or too much fuel.

In addition, fuel pressure is a major factor in this too. Low fuel pressure can cause more than just one cylinder to misfire. If the fuel pressure is too low, then the engine will run lean causing it to misfire. If this is the case, your computer may generate a P0171 or a P0300.

The Lover

Yes I have both codes , P0171 and P0300 codes , so if theres no leak , you think its the fuel pressure sensor or the fuel pump it self , by the way I found that c63 has two fuel pump , left and right

Quoted from

http://www.parts.com/parts/2009/Merc...gramCallOut=14

Thank you for helping

Ingenieur

check the pressure first at >1500 rpm
if it meets spec the pump is probably OK

the sensor is reading so I'm guessing it is OK

I'm betting on the pump
I think one pump transfers fuel from one side of the tank to the other
and the other feeds the engine fuel rail

my guess: pump was slowly failing leading to the misfires
finally got low enough to set the low pressure code and lean code
car has 80k miles on it, a failed fuel pump would not surprise me

The Lover

you mean that I should check the pressure at 1500 rpm while driving or just accelerating on P gear ?

roadtalontsi

Lots of realllllllllly bad information here guys....

the fuel pressure test says to test it at idle - hence the part where it says engine idling. clearly the fuel pressure actual value is not at the specified. Fuel pressure is regulated by the fuel pump control module. The fuel pump module sends pulse width modulated voltage to the pump not a constant power. Not vacuum diaphram, it's a returnless system - you'd be running a vacuum line all the way to the tank. So you've got a few possibilities.... bad pump, bad sensor, bad fuel pump control module.

This car has 2 fuel pumps. Used on an as needed basis, I believe it actually has a fuel pump module for each pump but its been a while so forgive me if thats wrong. Neither pump transfers fuel from each side of the saddle, this is done with syphoning. at 1/2 a tank it should start transfering all the fuel to the right side of the tank - passenger side, where the pumps are.

Just dont go jumping a constant 12v to the fuel pumps as this will fry them. The car actually will run suprisingly well on one pump, It'll only throw the low pressure code under full load if thats the case though.

I dont understand how you guys have access to xentry and then claim the "stealership" is too expensive where are ya'll getting xentry/das machines?