Cold Start Emission Reduction Monitoring System and Method

Abstract

An engine emissions diagnostic is disclosed that utilizes parameters correlating to catalyst temperature to identify when an indication of degraded performance may be generated.

1 . A method for controlling a vehicle having an engine, the engine having an exhaust with an emission control device, comprising:
 during an engine start, at least temporarily adjusting an operating parameter of the engine to increase exhaust mass flow or temperature when needed to more rapidly heat the emission control device;   estimating temperature of the emission control device during said engine start; and   comparing said estimated temperature to a reference catalyst temperature required to achieve an emission threshold.   
   
   
       2 . The method of  claim 1  wherein said reference catalyst temperature is based on a desired engine idle speed. 
   
   
       3 . The method of  claim 2  wherein said reference catalyst temperature is further based on an estimated airflow based on the desired engine speed. 
   
   
       4 . The method of  claim 3  wherein said reference catalyst temperature is based on an expected spark value for current conditions. 
   
   
       5 . The method of  claim 4  wherein actual spark timing is adjusted based on fuel quality. 
   
   
       6 . The method of  claim 1  wherein said emission threshold is based on engine coolant temperature at start. 
   
   
       7 . A method for controlling a vehicle having an engine, the engine having an exhaust with an emission control device, comprising:
 during an engine start, at least temporarily adjusting at least engine airflow and spark timing to increase exhaust mass flow and temperature when needed to more rapidly heat the emission control device;   overriding at least one of said engine airflow and spark timing adjustments to compensate for an operating condition; and   setting a diagnostic indication when said override has caused temperature of the emission control device to be lower than desired to meet an emission level.   
   
   
       8 . A method for controlling a vehicle having an engine, the engine having an exhaust with an emission control device, comprising:
 during an engine cold start, at least temporarily adjusting at least engine airflow and spark timing to increase exhaust mass flow and temperature when needed to more rapidly heat the emission control device;   overriding at least one of said engine airflow and spark timing adjustments to compensate for fuel quality effects on combustion; and   setting a diagnostic indication when said override has caused temperature of the emission control device to be lower than desired to meet an emission level.   
   
   
       9 . The method of  claim 8  wherein said override compensates for hesitation fuel. 
   
   
       10 . The method of  claim 8  wherein said override compensates for engine speed falling below a selected engine speed profile during said start. 
   
   
       11 . The method of  claim 8  wherein said diagnostic indication sets a code in a controller of the vehicle. 
   
   
       12 . The method of  claim 8  wherein said emission level is based on engine coolant temperature at start.