Misfire cylinders 4, 5 and 6?

KHALEDYOUNES

MEMBER
2012 MERCEDES BENZ C280
6 CYL
2WD
AUTOMATIC
150,000 MILES

Hello,

I have a misfire 4, 5, 6.
I have changed sparks plugs, changed and reversed coil, changed all fuel injectors, and nothing changed. I checked on the m e of the car (brain of the car) and nothing unusual, but I noticed that when I unplugged the MAF the car ran way better than when the MAF is plugged in.
That's why I changed the MAF and the sensor and nothing changed.
What should I do next?
Thank you

3 Replies

JACOBANDNICKOLAS

MECHANIC
109,724 POSTS

Hi,

When you disconnect the MAF, the engine goes into a predetermined setting allowing the engine to continue running.

When you do this, does the engine run properly? Have you checked for engine vacuum leaks that can affect the MAF? If not, here is a link that explains how it's done:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Let me know if you find anything.

Take care,

Joe

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Sunday, February 5th, 2023 AT 5:22 PM

KHALEDYOUNES

MEMBER
3 POSTS

Hello Joe,

I forgot 2 mention that I am working on cars 2 years from now.
I did a smoke test to find for any leaks.
And no leaks were found.
So, I took it to a technician and told me the pressure in the engine is incorrect, but how can it be incorrect and when I unplug the MAF cars works 70% better. Is that logical?
I am thinking of a bad catalytic converter.
What do you think?
Thank you

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Monday, February 6th, 2023 AT 1:14 AM

JACOBANDNICKOLAS

MECHANIC
109,724 POSTS

Hi,

What pressure in the engine was he referring to? Was it engine compression, vacuum, exhaust back pressure, or crankcase pressure?

Let me know.

Joe

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Monday, February 6th, 2023 AT 7:59 PM