1990-1997 Ford Thunderbird Mass Air Flow (MAF) Sensor Contamination Service Tip

This TSB article is a diagnostic procedure to address vehicles that exhibit lean driveability MASS AIR FLOW (MAF) DISCUSSION symptoms and may or may not have any Diagnostic MAF sensors can get contaminated from a variety Trouble Codes (DTCs) stored in memory. of sources: dirt, oil, silicon, spider webs, potting
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compound from the sensor itself, etc. When a MAF sensor gets contaminated, it skews the transfer Follow the diagnostic procedures described in the function such that the sensor over-estimates air flow following Service Tip. The revised diagnostic at idle (causes the fuel system to go rich) and procedure is a more accurate means of diagnosing under-estimates air flow at high air flows (causes the symptoms. fuel system to go lean). This means Long Term Fuel Trims will learn lean (negative) corrections at idle and learn rich (positive) corrections at higher air If vehicle is driven at Wide Open Throttle (WOT) or high loads, the fuel system normally goes open loop rich to provide maximum power. If the MAF sensor is contaminated, the fuel system will actually be lean because of under-estimated air flow. During open loop fuel operation, the vehicle applies Long Term Fuel Trim corrections that have been learned during closed loop operation. These corrections are often lean corrections learned at lower air flows. This combination of under-estimated air flow and lean fuel trim corrections can result in spark knock/detonation and lack of power concerns at WOT and high loads.

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