Fuel driveability index detection

1. A method for fuel driveability index detection, the method comprising:

measuring an exhaust gas feedstream of an internal combustion engine with an oxygen sensor;

sensing an engine run condition;

obtaining a first input signal indicating a first oxygen sensor voltage;

obtaining a second input signal indicating a second oxygen sensor voltage at a period subsequent to said first input signal;

determining a first voltage trend based on said first input signal and said second input signal; and

determining whether said first voltage trend is decreasing at a rate greater than a first voltage threshold rate; and,

adjusting open loop fueling if said first voltage trend is decreasing at a rate greater than said first voltage threshold rate by adding fuel to combustion chambers of the internal combustion engine;

wherein said adjusting open loop fueling occurs within about five seconds of a cold start of the internal combustion engine.

2. The method of claim 1 , wherein said adding fuel is accomplished by increasing a base pulse width command to fuel injectors of said engine.

3. The method of claim 1 , wherein said sensing said engine run condition includes determining whether a software logic flag indicating an engine run condition has been set.

4. The method of claim 1 , further including determining whether closed loop fueling is disabled prior to obtaining said second input signal.

5. The method of claim 1 , further including determining whether engine coolant temperature is within a temperature operating window prior to obtaining said second input signal.

6. A system for fuel driveability index detection, the system comprising:

an engine;

an oxygen sensor disposed within the exhaust gas passage of said engine; and

an engine control module operatively connected to said engine

having a processor for:

obtaining a first input signal indicating a first oxygen sensor voltage, obtaining a second input signal indicating a second oxygen sensor voltage at a period subsequent to said first input signal,

determining a first voltage trend based on said first input signal and said second input signal,

determining whether said first voltage trend is decreasing at a rate greater than a first voltage threshold rate,

determining whether said first voltage trend is increasing at a rate greater than a second voltage threshold rate if said first voltage trend is not decreasing at a rate greater than said first voltage threshold rate,

determining whether an engine run timer is less than an engine run timer threshold if said first voltage trend is not increasing at a rate greater than said second voltage threshold rate,

obtaining a next input signal indicating a next oxygen sensor voltage if said engine run timer is less than said engine run timer threshold, determining a second voltage trend based on said first input signal and said next input signal,

determining whether said second voltage trend is decreasing at a rate greater than said first voltage threshold rate,

setting a software logic flag indicating a low driveability index if said first voltage trend is increasing at a rate greater than said second voltage threshold rate, and

setting a software logic flag indicating a high driveability index if said second voltage trend is decreasing at a rate greater than said first voltage threshold rate.

7. The system of claim 6 , further including said processor adjusting open loop fueling if said second voltage trend is decreasing at a rate greater than said first voltage threshold rate.