Abstract: Provided is a method and circuit for detecting cylinder misfire in an internal combustion engine having an ignition system including an ignition device, an ignition coil having a primary and a secondary winding, and a pair of spark plugs having respective gaps. As disclosed, the circuit is operative to separate spark current and ionization current to improve detection of cylinder misfire. The circuit includes power supply means for supplying voltage to the circuit to generate ion current across the spark plug gaps and voltage limiting means for isolating said power supply means from said ignition coil. There is also included negative voltage clamping means in electrical contact with the ignition coil secondary winding for clamping selected negative voltages generated during ignition.

Abstract: A control system (10) controls fuel injected into an internal combustion engine (14) having a fuel vapor recovery system (74) coupled to the air/fuel intake. To achieve stoichiometric combustion, delivery of liquid fuel is trimmed by a feedback variable (32) responsive to an exhaust gas oxygen sensor (26) and a learned value (40) representing quantity of recovered fuel vapor. Learning (40) is inhibited when an indication is provided of air/fuel operation rich of stoichiometry which is caused by factors other than vapor recovery.

Abstract: An idle speed control system includes a bypass throttling device coupled in parallel with the primary engine throttle. At the beginning of each idle speed control period, a controller generates an initial bypass throttle position from a desired or reference engine speed. Correction of this initial position is provided based upon a learned error between initial bypass throttle position and the actual position which is maintained by feedback control. The learning routine is enabled in response to an indication that the quantity of inducted fuel vapors is below a minimum value.

Abstract: A control system (10) controls the induction of fuel injected into an internal combustion engine (14) to achieve stoichiometric combustion. The control system includes a feedback controller (32) which generates a feedback variable by integrating the output of an exhaust gas oxygen sensor (26). Integration is inhibited in response to an indication of a rich air/fuel offset.

Abstract: A control system (10) controls both engine idle speed and purge flow through a fuel vapor recovery system (86) into an air/fuel intake (54) of the engine. A bypass throttle valve (66) connected in parallel with a primary engine throttle (62) is controlled by a feedback variable related to a difference between actual idle speed and desired idle speed. Purge flow is reduced when the bypass throttle position falls below a dead band provided stoichiometric air/fuel control is maintained.

Abstract: A control system (10) controls both engine idle speed and purge flow through a fuel vapor recovery system (86) into an air/fuel intake of the engine. A bypass throttle valve (72) connected in parallel with a primary engine throttle (62) is controlled by a feedback variable (ISFV) related to a difference between actual idle speed and desired idle speed. Purge flow (pdc) is reduced when the bypass throttle position falls below a dead band provided stoichiometric air/fuel control is maintained.

Abstract: A system and method for controlling operation of an engine wherein a fuel vapor recovery system is coupled between an air/fuel intake and a fuel supply system. An air/fuel ratio indication is provided by a proportional plus integral feedback controller coupled to a two-state exhaust gas oxygen sensor. In response to the air/fuel ratio indication and a measurement of inducted air flow, a base fuel command is generated. To compensate for purging of fuel vapors, a reference air/fuel ratio is subtracted from the air/fuel ratio indication and the resulting error signal generated. This compensation factor represents a learned value which is directly related to fuel vapor concentration, and it is subtracted from the base fuel command to correct for induction of fuel vapors. At initiation of fuel vapor purging, the rate of purge flow is incremented a predetermined amount with each change in state of the exhaust gas oxygen sensor.

Abstract: A system and method for controlling operation of an engine having a fuel vapor recovery system coupled between a fuel supply system and engine air/fuel intake. In response to a two-state exhaust gas oxygen sensor (EGO sensor), a feedback controller generates a desired fuel charge. This feedback controller is also responsive to an adaptive learning controller which provides corrections for long term air/fuel offsets caused by such factors as fuel injector variances. An adaptive fuel vapor learning controller measures fuel vapor concentration during purging operations of the fuel vapor recovery system. This adaptive fuel vapor learning controller provides a fuel vapor correction factor which is subtracted from the desired fuel charge to maintain proper air/fuel ratio operation during a fuel vapor purge. Purging operations are disabled when the measurement of fuel vapor concentration is below a preselected value. At that time, the offset learning controller is enabled for a preselected time.