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Originally posted by LordBiotree:
The maf will either lean or richen out the system. The maf will not cause the engine to run rough or not at all.

I would change out the ecu. A guy at work has a mustang. Kept having problems with the engine running rough, cutting out and eventually got to the point to where the car would not start.

Turned out there was a ground fried inside the ecu. Changed out ecu and everything is fine.

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The maf will either lean or richen out the system. The maf will not cause the engine to run rough or not at all.

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Mass Flow
By contrast, Mass Air Flow (MAF) systems use a sensor mounted in front of the throttle body that directly measures the amount of air inducted into the engine. The most common type of mass-flow sensor is the hot wire design: Air flows past a heated wire that’s part of a circuit that measures electrical current. Current flowing through the wire heats it to a temperature that is always held above the inlet air temperature by a fixed amount. Air flowing across the wire draws away some of the heat, so an increase in current flow is required to maintain its fixed temperature. The amount of current needed to heat the wire is proportional to the mass of air flowing across the wire. The mass-air meter also includes a temperature sensor that provides a correction for intake air temperature so the output signal is not affected by it.

The MAF sensor’s circuitry converts the current reading into a voltage signal for the computer, which in turn equates the voltage value to mass flow. Typical MAF systems also use additional sensors similar to those found in Speed Density systems. Once the electronic control module (ECM) knows the amount of air entering the engine, it looks at these other sensors to determine the engine’s current state of operation (idle, acceleration, cruise, deceleration, operating temperature, and so on), then refers to an electronic map to find the appropriate air/fuel ratio and select the fuel-injector pulse width required to match the input signals.

GM used MAF sensors on the turbo Buick V-6 Grand National, ’85-’89 TPI, ’94-’98 LT1, ’96 LT4, and all LS1 engines. Ford has used MAF metering on ’88 California 5.0L engines and all ’89-and-later V-8 engines.

MAF systems are much more flexible in their ability to compensate for engine changes since they actually measure airflow instead of computing it based on preprogrammed assumptions. They are self-compensating for most reasonable upgrades, as well as extremely accurate under low-speed, part-throttle operation. On the other hand, the MAF meter, mounted as it is ahead of the throttle-body, can become an airflow restriction on high-horsepower engines. On nonstock engine retrofits or EFI conversions on engines never produced with fuel injection, it may be hard to package an MAF meter within the confines of the engine bay and available intake manifolding.