MAF is the hot film mass airflow sensor. It measures the amount of air entering the engine. It can cause some running problems if it is functioning incorrectly and it will fail inspection if it is brought for inspection at a state that does emmissions testing.

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Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record