Low fuel consumption and codes P0300, P0301, P0302, P0304, and P0174?

Hi,

The P0174 indicates a lean fuel mixture on bank 2. Interestingly, the misfire codes you have are for bank 1 other than the P0300 which is a random misfire.

A lean fuel mixture can be the result of several things. For example, plugged fuel injectors, an exhaust leak on bank 2 before the catalytic converter, faulty oxygen sensors, a weak fuel pump or faulty regulator, or even the ECM. As far as the fuel pump is concerned, in most cases, it will not be limited to only one side of the engine.

So, in this case, here is where I would start. First, check to see if you hear an exhaust leak at the engine exhaust manifold (one side only). If you hear nothing, then I need you to check for engine vacuum leaks.

Here is a link that explains how that is done:

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

Also, if you have or have access to a live data scan tool, let me know what the short-term fuel trims are with the engine at operating temperature.

Let me know if you have questions and what you find.

Take care,

Joe

Hello, thanks for the reply, my problem is solved by cleaning all 8 fuel injectors, now fuel trims readings are good and within specifications of 10 +-
But i have one question as i noticed that bank 2 sensor 2 post cat o2 sensor is mirroring the pre cat o2 sensors readings on same bank as it is fluctuating between 0 - 8 volts , these reading are on idle, does that have any impact on my fuel consumption or on my car engine life, or this sensor only for monitoring catalytic converter' s efficiency? Cats are expensive and i don't want to change it.
BTW now i don't have any CEL codes on my car.

Hi,

Thanks for the update. I'm glad to hear the problem is resolved.

As far as the sensors being the same, it is likely due to the converter itself. If the catalytic converter is not functioning properly, it won't effectively reduce emissions. This could lead to similar oxygen sensor readings before and after the catalytic converter.

If it is running properly and there are no codes, drive it. If the converter is faulty, it will eventually set a P0420 or P0421. If it doesn't, I wouldn't worry about it.

Let me know if anything happens.

Joe