Apparatus and method for diagnosing an engine system

A method of diagnosing an engine system of a vehicle, the method comprising:

• determining, by a controller, whether an entry condition diagnosing the engine system is satisfied based on state information of the vehicle;
• executing, by the controller, a diagnostic logic diagnosing the engine system when the entry condition is satisfied and an idle time after an engine is started exceeds a first time;
• determining, by the controller, an ignition efficiency diagnosis index by dividing an ignition efficiency control difference average while the engine is in an idle state by an ignition efficiency control target average while the engine is in the idle state;
• and
• determining, by the controller, that the engine system is abnormal when the ignition efficiency diagnosis index is less than a set fault diagnosis reference value.

An engine system of a vehicle, the system comprising:

• an engine;
• a catalytic converter configured to purify an exhaust gas generated from the engine;
• an exhaust system configured to discharge the exhaust gas purified through the catalytic converter;
• and
• a controller configured to:
• determine whether an entry condition diagnosing the engine system is satisfied based on state information of the vehicle,
• execute a diagnostic logic diagnosing the engine system when the entry condition is satisfied and an idle time after the engine is started exceeds a first time,
• determine an ignition efficiency diagnosis index by dividing an ignition efficiency control difference average while the engine is in an idle state by an ignition efficiency control target average while the engine is in the idle state, and
• determine that the engine system is abnormal when the ignition efficiency diagnosis index is less than a set fault diagnosis reference value.