Other Category problem
1996 Ford Explorer 6 cyl Four Wheel Drive Automatic 130000 miles
I've replaced the O2 sensors and fuel pump on my Explorer. I again have my Check Engine Light on with the codes 171 and 174 showing. It seems every time my Check Engine Light comes on (almost yearly), it has to do with my fuel system. Fuel too lean and fuel too rich seem to be the most common - which is what it's showing now. How can I fix this on a long term basis? Is this a common problem?
On many Fords, a P0171 and/or P0174 Lean Code may sometimes appear because of a bad Differential Pressure Sensor (DPFE). This sensor monitors EGR flow, and is located on the engine near the EGR valve. There are two hoses that connect the sensor to the tube that runs from the exhaust manifold to the EGR valve. The sensor misreads EGR flow and the computer increases EGR which has a leaning effect on the fuel mixture. The fix is to replace the DPFE sensor.
A lean fuel condition can be caused by: * Low fuel pressure due to a weak pump or leaky fuel pressure regulator. (Use a fuel pressure gauge to check fuel pressure at idle)
* Dirty fuel injectors. (Try cleaning the injectors)
* Vacuum leaks at the intake manifold, vacuum hose connections or throttle body. (Use a vacuum gauge to check for low intake vacuum)
* Leaky EGR valve. (Check operation of EGR valve)
* Leaky PCV Valve or hose. (Check valve and hose connections)
* Dirty or defective Mass Airflow Sensor (MAF). (Try cleaning the MAF sensor wires or filament with aerosol electronics cleaner. Do NOT use anything else to clean the sensor, and do not touch the sensor wires)