Air Measurement System

WARNING: This page does not describe the selected car, but rather 31 other vehicles, including the 2006 Mercury Mountaineer, 2006 Mercury Monterey, 2006 Mercury Montego, 2006 Mercury Milan, and 2006 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, contaminated 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).

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 less than what the MAF sensor is indicating to the PCM. For example, with a contaminated MAF sensor, the engine will run rich at idle because the PCM will deliver fuel for more air than is actually entering the engine.

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