Diagnosis of General Engine Failures

Engine does not crank when attempting to start
1 Battery terminals are corroded, or wire terminal connections are loose (refer to Maintenance and Tune-up section).
2 Battery is discharged or faulty (refer to Maintenance and Tune-up section).
3 Shift selector is not in "P" position on AT/CVT (refer to Transmission section), or clutch pedal is not fully depressed (refer to Clutch and Drive Shafts section).
4 Starting circuit wiring is broken or otherwise damaged, or circuit connector terminals are loose (refer to Engine Electrical or Body Electrical section).
5 Starter pinion gear is jammed in the flywheel ring gear (refer to Engine Electrical section).
6 Starter solenoid relay has failed (refer to Engine Electrical section).
7 Starter motor is faulty (refer to Engine Electrical section).
8 Ignition switch is faulty (refer to Body Electrical section).
9 Starter pinion gear teeth or flywheel ring gear teeth are broken or worn (refer to Engine and Engine Electrical sections).

Engine cranks but does not start
1 Fuel tank is empty.
2 Battery is discharged (engine cranks too slowly) (refer to Engine Electrical section).
3 Battery terminals are corroded, or wire terminal connections are loose (refer to Maintenance and Tune-up section).
4 Fuel is leaking through injector(s), fuel pump is faulty, or fuel pressure regulator is faulty (refer to Fuel and Exhaust Systems section).
5 Fuel is not reaching the fuel rail (refer to Fuel and Exhaust Systems section).
6 Other fuel supply system faults are present (refer to Fuel and Exhaust Systems section).
7 Ignition system components are wet or damaged (refer to Engine Electrical section).
8 Spark plugs are worn or damaged, or spark plug gaps are incorrect (refer to Maintenance and Tune-up section).
9 Starting circuit wiring is broken or otherwise damaged, or circuit connector terminals are loose (refer to Engine Electrical section).
10 Ignition timing is incorrect due to loose distributor mounting (refer to Engine Electrical section).
11 Ignition circuit wiring is broken or otherwise damaged, circuit connector terminals are loose, or ignition coil is faulty (refer to Engine Electrical section).
12 Timing belt is broken or worn (refer to Engine section).
13 Fuel pump relay and/or its wiring is faulty (refer to Engine section).
14 Mechanical engine damage is present (for example, camshaft drive) (refer to Engine section).

Hard starting when engine is cold
1 Battery is discharged (refer to Maintenance and Tune-up section).
2 Fuel supply system is faulty (refer to Fuel and Exhaust Systems section).
3 Fuel is leaking through injector(s) (refer to Fuel and Exhaust Systems section).
4 Distributor cap has carbon tracking breakdown (refer to Engine Electrical section).
5 Ignition timing is incorrect (refer to Engine Electrical section).
6 Battery terminals are corroded, or wire terminal connections are loose (refer to Maintenance and Tune-up section).
7 Spark plugs are worn or damaged, or spark plug gaps are incorrect (refer to Maintenance and Tune-up section).
8 Compression pressure is low (refer to Engine section).

Hard starting when engine is hot
1 Air filter element is dirty or airflow is otherwise restricted (refer to Maintenance and Tune-up section).
2 Fuel injection system is faulty (fuel does not reach injectors) (refer to Fuel and Exhaust Systems section).
3 Battery terminals are corroded (especially ground) (refer to Maintenance and Tune-up section).
4 Compression pressure is low (refer to Engine section).
5 Ignition timing is incorrect (refer to Engine Electrical section).
6 Evaporative emission control (EVAP) system is faulty (refer to Engine Control section).

Starter engagement is difficult or accompanied by abnormal noise
1 Starter pinion gear teeth or flywheel ring gear teeth are broken or worn (refer to Engine and Engine Electrical sections).
2 Starter mounting bolts are loose or missing (refer to Engine Electrical section).
3 Starter internal components are worn or damaged (refer to Engine Electrical section).

Engine starts but stalls immediately
1 Ignition circuit wiring is broken or otherwise damaged, or circuit connector terminals at the distributor, ignition coil, or alternator are loose (refer to Engine Electrical section).
2 Fuel starvation of injector(s) (refer to Maintenance and Tune-up and Fuel and Exhaust Systems sections).
3 Vacuum leaks through the intake manifold to throttle body gasket (refer to Maintenance and Tune-up and Fuel and Exhaust Systems sections).

Oil drips under engine after parking
1 Leaks through oil pan gasket or drain plug (refer to Engine section).
2 Leaks through oil pressure switch seal (refer to Engine section).
3 Leaks through cylinder head gaskets (refer to Engine section).
4 Leaks through engine shaft seals (refer to Engine section).

Idle speed is unstable
1 Vacuum leaks are present (refer to Engine and Fuel and Exhaust Systems sections).
2 EGR valve is faulty (refer to Engine Control section).
3 Air filter element is clogged (refer to Maintenance and Tune-up section).
4 Fuel pump does not deliver required fuel flow (refer to Fuel and Exhaust Systems section).
5 Fuel pulsation damper is faulty (refer to Fuel and Exhaust Systems section).
6 Cylinder head gasket is leaking (refer to Engine section).
7 Timing belt or timing gears are worn (refer to Engine section).
8 Timing belt tension is incorrectly adjusted (refer to Engine section).
9 Camshaft lobes are worn (refer to Engine section).
10 Spark plugs are worn or damaged, or spark plug gaps are incorrect (refer to Maintenance and Tune-up section).
11 Compression pressure is low or uneven between cylinders (refer to Engine section).
12 Injector(s) are clogged (refer to Fuel and Exhaust Systems section).
13 Powertrain mount control system malfunctions (refer to Engine section).

Engine misfires at idle
1 Spark plugs are worn or damaged, or spark plug gaps are incorrect (refer to Maintenance and Tune-up section).
2 Spark plug high-tension (HT) wires are faulty (refer to Maintenance and Tune-up section).
3 Vacuum leaks are present (refer to Maintenance and Tune-up section).
4 Ignition timing is incorrect (refer to Maintenance and Tune-up section).
5 Compression pressure is low or uneven between cylinders (refer to Engine section).
6 Fuel injection/engine control system is faulty (refer to Fuel and Exhaust Systems and Engine Control sections).
7 Crankcase ventilation hoses are damaged, worn, or disconnected (refer to Fuel and Exhaust Systems section).
8 Distributor cap is cracked or has carbon tracking inside (refer to Engine Electrical section).

Engine misfires under load in gear
1 Fuel filter is clogged (refer to Maintenance and Tune-up section).
2 Fuel pressure is low (refer to Fuel and Exhaust Systems section).
3 Spark plugs are worn or damaged, or spark plug gaps are incorrect (refer to Maintenance and Tune-up section).
4 Ignition timing is incorrect (refer to Engine Electrical section).
5 Distributor cap is cracked, has carbon tracking inside, or HT wire connections are loose (refer to Maintenance and Tune-up and Engine Electrical sections).
6 Spark plug high-tension (HT) wires are faulty (refer to Maintenance and Tune-up and Engine Electrical sections).
7 Exhaust emission control system components are faulty (refer to Engine Control section).
8 Compression pressure is low or uneven between cylinders (refer to Engine section).
9 Ignition system is faulty, or wiring connections are loose (refer to Engine Electrical section).
10 Vacuum leaks are present in the fuel injection system, intake manifold, air control valve, or vacuum hoses (refer to Fuel and Exhaust Systems and Engine Control sections).
11 Fuel pump is faulty, or its pressure output is low (refer to Fuel and Exhaust Systems section).
12 Fuel tank venting is restricted, or fuel lines are blocked (refer to Fuel and Exhaust Systems section).

Engine speed is unstable during acceleration
1 Spark plugs are worn or damaged, or spark plug gaps are incorrect (refer to Maintenance and Tune-up section).
2 Fuel injection system is faulty (refer to Fuel and Exhaust Systems section).
3 Fuel filter is clogged (refer to Fuel and Exhaust Systems section).
4 Ignition timing is incorrect (refer to Engine Electrical section).
5 Air leaks are present in the intake system (refer to Engine and Fuel and Exhaust Systems sections).
6 Injector wiring connector(s) are loose (refer to Fuel and Exhaust Systems section).
7 Engine control module (ECM) or one of the engine control system sensors is faulty (refer to Engine Control section).

Engine surges with accelerator pedal held steady
1 Air leaks are present in the intake system (refer to Engine and Fuel and Exhaust Systems sections).
2 Fuel pump is faulty (refer to Fuel and Exhaust Systems section).
3 Injector wiring connector(s) are loose (refer to Fuel and Exhaust Systems section).
4 Engine control module (ECM) or one of the engine control system sensors is faulty (refer to Engine Control section).

Engine stalls spontaneously
1 Idle speed is incorrectly set (refer to Maintenance and Tune-up section).
2 Fuel filter is clogged, or water has entered the fuel system (refer to Maintenance and Tune-up and Fuel and Exhaust Systems sections).
3 Ignition system components are wet or damaged (refer to Engine Electrical section).
4 Exhaust emission control system components are faulty (refer to Engine Control section).
5 Spark plugs are worn or damaged, or spark plug gaps are incorrect (refer to Maintenance and Tune-up section).
6 Spark plug high-tension (HT) wires are faulty (refer to Maintenance and Tune-up section).
7 Vacuum leaks are present at the throttle body, intake manifold, or connecting hoses (refer to Engine and Fuel and Exhaust Systems sections).
8 Valve clearance adjustment is incorrect (refer to Maintenance and Tune-up section).
9 Fuel pump is faulty, or its pressure output is low (refer to Fuel and Exhaust Systems section).
10 Fuel tank venting is restricted, or fuel lines are blocked (refer to Fuel and Exhaust Systems section).

Engine power output is reduced
1 Ignition timing is incorrect (refer to Engine Electrical section).
2 Distributor shaft play is excessive (refer to Engine Electrical section).
3 Distributor rotor, distributor cap, or its wiring is faulty (refer to Maintenance and Tune-up and Engine Electrical sections).
4 Spark plugs are worn or damaged, or spark plug gaps are incorrect (refer to Maintenance and Tune-up section).
5 Fuel injection system is faulty (refer to Fuel and Exhaust Systems section).
6 Ignition coil is faulty (refer to Engine Electrical section).
7 Brakes are dragging (refer to Brake System section).
8 Transmission fluid (ATF) level is low on AT/CVT (refer to Maintenance and Tune-up section).
9 Clutch is slipping (refer to Clutch and Drive Shafts section).
10 Fuel filter is clogged, or water has entered the fuel system (refer to Maintenance and Tune-up and Fuel and Exhaust Systems sections).
11 Exhaust emission control system is faulty (refer to Engine Control section).
12 Compression pressure is low or uneven between cylinders (refer to Engine section).
13 Exhaust system is blocked (refer to Fuel and Exhaust Systems section).
14 Fuel pump is faulty, or its pressure output is low (refer to Fuel and Exhaust Systems section).

Backfiring occurs in the exhaust system
1 Exhaust emission control system is not functioning correctly (refer to Engine Control section).
2 Ignition timing is incorrect (refer to Engine Electrical section).
3 Secondary ignition circuit fault is present (spark plugs, distributor cap or rotor, etc.) (refer to Engine Electrical section).
4 Fuel injection system is faulty (refer to Fuel and Exhaust Systems section).
5 Vacuum leaks are present at the throttle body, intake manifold, or connecting hoses (refer to Fuel and Exhaust Systems section).
6 Valve clearance adjustment is incorrect, or valves are sticking (refer to Maintenance and Tune-up section).

Knocking or pinging occurs during acceleration or under increased load, caused by early ignition or detonation
1 Wrong grade of fuel has been added.
2 Ignition timing is incorrect/ignition system is faulty (refer to Engine Electrical section).
3 Fuel injection system is faulty (refer to Fuel and Exhaust Systems section).
4 Spark plugs or HT wires are damaged (refer to Engine Electrical section).
5 Distributor components are worn (refer to Engine Electrical section).
6 EGR valve is not functioning correctly (refer to Engine Control section).
7 Vacuum leaks are present (refer to Engine and Fuel and Exhaust Systems sections).
8 Excessive carbon buildup is present in the engine (refer to Engine section).

Engine oil pressure warning lamp remains on with engine running
1 Oil level is low, or wrong grade of oil has been added (refer to Maintenance and Tune-up section).
2 Short circuit in the wiring harness (refer to Body Electrical section).
3 Oil pressure switch is faulty (refer to Engine section).
4 Engine bearings and/or oil pump are worn (refer to Engine section).
5 Engine operating temperature is excessively high (refer to Cooling and Heating Systems section).
6 Oil pickup screen is clogged (refer to Engine section).

Engine continues to run after ignition is switched off
1 Idle speed is set too high (refer to Engine Electrical section).
2 Engine operating temperature is excessively high (refer to Cooling and Heating Systems section).
3 Ignition timing adjustment is incorrect (refer to Engine Electrical section).
4 Excessive carbon buildup is present in the engine (refer to Engine section).
5 Fuel system is faulty (refer to Fuel and Exhaust Systems section).