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It is not a fuel filter. If the left bank was lean the right would be also since the complete engine is fed from a single line to the injectors. Your O2 sensor is probably throwing the code to set the check engine light. The O2 sensors control the amount of fuel fed to the engine. Most Fords use an upstream and a down stream O2 sensor. From what you are describing I am betting your vehicle has way over 100,000 miles on it. The O2 sensors start going out after this point. They are subject to heat extremes and contamination from burned oil deposits and carbon and or fuel additives that you place into your fuel tank. If the code is reading or giving you a "lean" condition more than likely your upstream O2 sensor has bit the bullet finally.
It's really impossible to diagnose something like this. You're running lean...so? You could have a bad o2 sensor reading the exhaust stream wrong and commanding the PCM to go lean..could be a bad or gunked up injector, fuel pump, fuel filter...too many things to Diagnose like this. +
O2 Sensor codes rarely mean that the O2 Sensors are defective. Most of the time, the O2 sensors are reporting a problem that is occuring somewhere else in the system. If your are getting a code that says "O2 sensor lean" that means that someting on that side of the engine is causing that side to be running lean. This is usually caused by a vacuum leak, but may also be caused by bad injectors or low fuel pressure. If BOTH sides are reporting lean O2 Sensor codes at the same time, it is something wrong that affects both sides of the engine including vacuum leaks in the main hoses tied into the intake manifold including the PCV hose and the Brake Booster Vacuum hose or the brake booster itself, or the Mass Airflow Sensor. Defective Engine Coolant Temperature sensors can also cause these codes. If the code you are getting is a "O2 Sensor Rich" code, it is caused by something that is making the engine run rich. This could be a sticking injector, a failed Fuel Pressure Regulator, or an O2 Sensor circuit that is shorted to voltage, or a malfunctioning Mass Airflow Sensor. If you want to save a lot of money and frustration, learn this: Fault codes NEVERtell you what parts to replace. Fault codes only tell you which of the many systems monitored by the computer are operating outside their expected ranges or "Window of Operation". It is up to the person diagnosing the vehicle to test the system that is reporting the malfunction and determine the cause of the failure and repair as necessary.
those codes are for lean engine condition look for vac leaks at the back of engine to the pcv valve could hear hissing noise with engine running also check egr valve to be stuck open also when was last fuel filter changed? hope this helps .
This might help. It looks like you O2 sencor had gone bad or the signal has and causing multiple mis fire. according to your codes.
PO171 System too Lean (Bank 1 PO174 System too Lean (Bank 2) PO300 Random/Multiple Cylinder Misfire Detected Causes of PO300 Fuel injectors, related wiring, sensors and computer issues Running out of gas, or poor fuel quality Evaporative emissions system (EVAP) concerns: fuel vapors leaking into engine Incorrect Fuel Pressure EGR system concerns I'ld start with chaning the O2 sensors first but sheck for bad wire connection. Hope this helps and good luck