Closed loop control has the ability to provide approximately ± 20% correction range from the basic fuel calculation. This allows the system to easily compensate for small mixture imbalances; however, major air/fuel imbalances (such as large vacuum leaks, leaky fuel pressure regulator, etc.) may push its correction abilities to the limit without bringing the air/fuel mixture back to the "ideal" ratio. If this occurs, whether the mixture is driven too rich or too lean, increased emission levels and driveability problems may result from the systems inability to correct for these problems.
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