SYSTEMS AND METHODS FOR AN AIR-FUEL RATIO IMBALANCE MONITOR

摘要

Methods and systems are provided for detecting an air-fuel imbalance based on output from multiple degradation monitors. In one example, a method comprises, during feedback engine air-fuel ratio control responsive to output of an exhaust gas sensor positioned downstream of a catalyst, indicating a cylinder imbalance responsive to a catalyst transfer function determined only within a specified frequency range based on the exhaust gas sensor output after determining that the catalyst is nominal, and adjusting an actuator in response to the indicated cylinder imbalance. In this way, air-fuel ratio imbalances may be accurately identified and mitigated, thereby reducing emissions.

主权项

1. A method, comprising:
during feedback engine air-fuel ratio control responsive to output of an exhaust gas sensor positioned downstream of a catalyst, indicating a cylinder imbalance responsive to a gain magnitude of a catalyst transfer function above a threshold, the catalyst transfer function determined only within a specified frequency range based on the exhaust gas sensor output; and adjusting an injection pulse width of at least one fuel injector responsive to the indicated cylinder imbalance.