How do I correct the Check engine light on my 1998 Mazda 626 with the code of p0171?

Answer 1

Hi, I have the same problem with my 2000 Mazda 626. Still working on the problem, but I found this helpful:

http://www.aa1car.com/library/problem_hesitation.htm

DIAGNOSTIC TIPS FOR P0171 OR P0174 LEAN TROUBLE CODES A code P0171 or P0174 (or both) indicate the engine is running lean. This means there is too much air and/or not enough fuel. If you have a scan tool that can display Short Term Fuel Trim (STFT), you can confirm the engine is running lean by looking at the STFT at idle. If STFT is greater than about 10 to 12, the engine is running LEAN. Increase engine speed to 1600 to 2000 rpm and hold for a minute or so, then recheck the STFT value. If it has dropped 3 or 4 points or more, the lean problem is due to a vacuum leak (vacuum leaks have more of an impact on the idle fuel mixture than the cruise mixture). If the STFT valve is still the same, the problem is probably sensor-related (dirty or bad MAF sensor, or bad MAP sensor), or is due to low fuel pressure. The next steps would be to use the scan tool to look at the airflow and MAP sensor readings, and to check fuel pressure. 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. (Check for vacuum leaks)

* Leaky EGR valve. (Check the operation of the 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)

* TIP: 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.

* TIP: For information about other causes of P0171 and P0174 lean codes on Ford Windstar, Click Here

REPAIRS Repairs will depend on what is causing the hesitation. If the cause is fuel related, it may require cleaning the fuel injectors or fixing a vacuum leak. If the cause is ignition related, it may require replacing the spark plugs and plug wires