Engine control strategy

Abstract

In at least some implementations, a method of controlling engine idle speed includes comparing engine speed to a speed threshold where the speed threshold may include a range of speeds, if the engine speed is outside of the speed threshold, adjusting the timing of an ignition spark up to a threshold amount of ignition timing adjustment, and if the engine speed is not within said speed threshold after adjustment up to the threshold amount of ignition timing adjustment then adjusting the air/fuel mixture provided to the engine to bring the engine speed within said speed threshold.

1 . A method of controlling engine idle speed, comprising:
 comparing engine speed to a speed threshold where the speed threshold may include a range of speeds;   if the engine speed is outside of the speed threshold, adjusting the timing of an ignition spark up to a threshold amount of ignition timing adjustment; and   if the engine speed is not within said speed threshold after adjustment up to the threshold amount of ignition timing adjustment then adjusting the air/fuel mixture provided to the engine to bring the engine speed within said speed threshold.   
     
     
         2 . The method of  claim 1  wherein the air/fuel mixture adjustment may be provided in an amount sufficient to reduce the magnitude of a previously made ignition timing adjustment. 
     
     
         3 . The method of  claim 2  wherein when the ignition timing adjustment reaches the high side of the threshold amount of ignition timing adjustment the fuel mixture is leaned out to increase the engine speed. 
     
     
         4 . The method of  claim 2  wherein when the ignition timing adjustment reaches the low side of the threshold amount of ignition timing adjustment the fuel mixture is enriched to decrease the engine speed. 
     
     
         5 . The method of  claim 3  wherein the high side of the threshold amount of ignition timing adjustment is the maximum increase in spark advance within the threshold for ignition timing adjustment. 
     
     
         6 . The method of  claim 4  wherein the low side of the threshold amount of ignition timing adjustment is the maximum decrease in spark advance within the threshold for ignition timing adjustment. 
     
     
         7 . A method of detecting engine cycles, comprising:
 determining the time for consecutive engine revolutions;   comparing the time of a revolution to a consecutive revolution;   repeating the comparison for a first threshold number of revolutions; and   determining if every other revolution is either faster or slower than the intervening revolutions for a second threshold number of revolutions.   
     
     
         8 . The method of  claim 7  wherein when the second threshold is satisfied an ignition spark is skipped based upon the engine revolution timing. 
     
     
         9 . The method of  claim 7  wherein if the second threshold is not satisfied within the first threshold number of engine revolutions, then an ignition spark is skipped every other engine revolution and then the engine speed is determined. 
     
     
         10 . The method of  claim 9  wherein if the engine speed has decreased below a threshold amount, the ignition event skipping is changed to the opposite engine revolutions. 
     
     
         11 . The method of  claim 9  wherein if the engine speed has not decreased below a threshold amount, the ignition event skipping is continued. 
     
     
         12 . The method of  claim 10  wherein after the ignition event skipping is changed, the fuel supply to the engine is adjusted to correspond to the engine intake cycle. 
     
     
         13 . The method of  claim 11  wherein in addition to continuing the ignition event skipping, the fuel supply to the engine is adjusted to correspond to the engine intake cycle. 
     
     
         14 . A method of controlling engine acceleration or deceleration, comprising:
 determining occurrence of an engine acceleration or deceleration;   adjusting ignition timing within preselected threshold limits during acceleration or deceleration of the engine; and   adjusting an air/fuel mixture delivered to the engine during acceleration and deceleration of the engine.   
     
     
         15 . The method of  claim 14  wherein the ignition timing is adjusted up to a threshold amount of adjustment either before or while the air/fuel mixture adjustment occurs. 
     
     
         16 . The method of  claim 14  wherein when an engine acceleration is determined the ignition timing is advanced and the air/fuel mixture is enriched. 
     
     
         17 . The method of  claim 14  wherein when an engine deceleration is determined the ignition timing is retarded and the air/fuel mixture is enriched. 
     
     
         18 . The method of  claim 16  wherein the air/fuel mixture is controlled by controlling a valve that reduces fuel flow to the engine and the air/fuel mixture is enriched by reducing the period of time that the valve reduces fuel flow to the engine. 
     
     
         19 . The method of  claim 17  wherein the air/fuel mixture is controlled by controlling a valve that reduces fuel flow to the engine and the air/fuel mixture is enriched by reducing the period of time that the valve reduces fuel flow to the engine.