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Hello Benz friends,

I have a 2007 s550 and my check engine light came on. I took the car to auto zone to get a reading and I was told I'm getting misfires in cylinders 5,6,&7 and the 02 sensor. I changed all the spark plugs out and the coils for 5,6,&7 but the light is still on. Another shop told me that it's my catalytic converter. Thanks for the help in advance!
 

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Hello Benz friends,

I have a 2007 s550 and my check engine light came on. I took the car to auto zone to get a reading and I was told I'm getting misfires in cylinders 5,6,&7 and the 02 sensor. I changed all the spark plugs out and the coils for 5,6,&7 but the light is still on. Another shop told me that it's my catalytic converter. Thanks for the help in advance!
How can they tell its your CAT? It needs to be rescan and check what codes are being thrown. I have an S550 and never heard of the CATS going back just like that but every car is also different because of fuel used and upkeep.
 

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Please post the codes that you received so we can help you troubleshoot. For example, there are specific codes tailored to each of the four O2 sensors.

How many miles on the car?
How long have you had the CEL light?
What are all of the symptoms? (i.e. rattling under the car at idle / low speed, loss of power under acceleration)

Coils are pretty reliable - O2 sensors should be replaced every 100,000 miles with Bosch.
 

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P0300 P0305 P0306 P0307 P0308 (Misfire in cylinders 5,6,7 & 8)

P0040 oxygen sensor signals swapped bank 1 sensor 1/ bank 2 sensor 1

P2A03 02 sensor circuit range/ performance bank 2 sensor 1

The car has 90,000 miles on it.

Having loss of power at times but sometimes I can cut the car of and start it back up and it will run fine.

Thanks for the reply guys
 

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At 90,000 miles, you are in the zone for needing new O2 sensors. They don't last forever, and I try to replace them at the 100,000 mile mark - because they can cause too rich of a mixture and cook the cats.

Bad O2 sensors can also play havoc with your engine's fuel air ratio mixture and potentially cause the problems that you are experiencing.

IMHO - that is where I would start since it is an upcoming replacement maintenance task. 4 sensors total at about $100 each for Bosch.

I am going to guess that your gas mileage is off.
 

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Under these conditions, if it were my car I'd change the front two O2 sensors with Bosch, and be ready to change the rear two sensors. Take note the sensors are not interchangeable between front and rear. Also, the CEL if not cleared with a scanner may take several drive cycles to clear on its own. Also, if the spark plugs are fouled with too rich a fuel mixture, they may take time to come back into normal operating range.

Your gas mileage should improve pretty quickly.

Good luck
 
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