Quote:
Originally Posted by mwebb
if there is less air because of a restriction , the restriction becomes the throttle . the ECM will provide only the amount of fuel to match the amount of air that it counts . the ECM counts the air flow with either a calculation in speed density systems or more directly with the input from the MAF sensor .
the ECM only provides fuel to match the counted air
the system DOES NOT run rich because of intake restrictions .
intake restrictions do reduce maximum power output by reducing the maximum
calculated load value
intake restrictions have zero effect on fuel to air mixture
and
zero effect on fuel trim
the system can change mixture based on load depending on it's design.
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My long term fuel trim is running 0.78-2.34% rich, and I have been considering three suspects. One is restriction from my 25% reduction in my WAI intake tube diameter. This comment suggests that's not the issue. My other suspects are my O2 sensors (very old they are) or dirty injectors.
But I have a question still about the restriction: what if the ECU does not have MAF sensor data and can't "count" the air? Many of the cars listed here at EM, such as mine, only have the throttle position sensor, IAT sensor, and the MAP sensor. Doesn't that change your argument about how the ECU reacts? And does it mean restriction could force the car to run rich more often?