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Home >> Ford >> 2000 >> Contour SE, 2.5 L, Standard >> Repair and Diagnosis >> External Pages >> Different car >> Section 763 (Engine Controls - Diagnostic Methods (Except Diesel & Hybrid)) >> Adaptive Fuel Diagnostic Trouble Codes Diagnostic Techniques >> DTC P0171/P0174: System Too Lean Diagnostic Aids >> Air Measurement System

Air Measurement System

WARNING: This page does not describe the selected car, but rather 32 other vehicles, including the 2005 Mercury Sable, 2005 Mercury Mountaineer, 2005 Mercury Monterey, 2005 Mercury Montego, and 2005 Mercury Mariner. However, it is still accessible from the selected car via links, so may be relevant.

With this condition, the engine will run rich or lean of stoichiometry (14.7:1 air/fuel ratio) if the PCM is not able to compensate enough to correct for the condition. One possibility is that the mass of air entering the engine is actually greater than what the MAF sensor is indicating to the PCM. For example, with a contaminated MAF sensor, the engine will run lean at higher RPM because the PCM will deliver fuel for less air than is actually entering the engine.

Examples: MAF sensor measurement is inaccurate due to a corroded connector, contamination or dirty connector. A contaminated MAF sensor will typically result in a rich system at low airflows (PCM will reduce fuel) and a lean system at high airflows (PCM will increase fuel).

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