NO START - COLD ENGINE
- Ensure battery is fully charged.
- Check spark plugs.
- Check fuel pump fuse(s).
- Ensure ignition timing and fuel pressure are correct.
- Check fuel injectors.
- Check crank and cam sensors (DIS system).
- Ensure timing belt/chain has not jumped.
- Ensure ignition coil resistance is correct.
- Ensure rotor, distributor and plug wires are okay.
- Check ignition control unit.
- Check coolant temperature sensor and connector.
- Check throttle position sensor and connector.
- Check airflow sensor.
- Check anti-theft system (if applicable).
NO START - WARM ENGINE
- Ensure fuel pressure is correct.
- Check for gasoline in oil.
- Ensure fuel injectors are not leaking.
- Check ignition and sensor wires for proper connection.
- Ensure spark plugs are not fouled.
- Check ignition and coil circuit.
- Check crank and cam sensors (DIS system).
- Check throttle position sensor and connector.
STARTS BUT STALLS
- Check coolant temperature sensor.
- Check ignition and sensor wires for proper connection.
- Check fuel injectors.
- Check throttle position sensor and connector.
- Check anti-theft system (if applicable).
- Check crank and cam sensors (DIS system).
HARD TO START - COLD ENGINE
- Check spark plugs.
- Check distributor (if applicable).
- Ensure fuel pressure is correct.
- Check ignition timing.
- Check throttle position sensor and connector.
ERRATIC IDLE - WARM-UP
- Check throttle position sensor and connector.
- Check coolant temperature sensor and connector.
- Ensure spark plugs are not fouled.
- Check ignition and sensor wires for proper connection.
- Check distributor (if applicable).
- Check ignition and coil circuit.
- Check intake system.
- Check crank and cam sensors (DIS system).
- Check MAP sensor.
- Check for contaminated fuel.
BACKFIRING
- Ensure ignition timing is correct.
- Ensure timing belt/chain has not jumped.
- Check distributor (if applicable).
- Check for gasoline in oil.
- Ensure fuel injectors are not leaking.
- Check spark plugs and plug wires.
- Check distributor cap and rotor (if applicable).
- Check ignition and coil circuit.
- Check crank and cam sensors (DIS system).
- Check throttle switch and connector.
- Check exhaust system.
INCORRECT IDLE SPEED
- Check fuel injectors.
- Check intake system for leaks.
- Check coolant temperature sensor.
- Check throttle position sensor and connector.
- Check distributor (if applicable).
- Check MAP sensor.
HESITATION - ACCELERATION
- Check ignition and sensor wires for proper connection.
- Check distributor cap for moisture (if applicable).
- Check distributor cap for carbon tracking (if applicable).
- Ensure spark plug wires are okay.
- Ensure spark plugs are not fouled.
- Check EGR valve operation.
- Check MAP sensor.
- Check throttle position sensor and connector.
- Check ignition and coil circuit.
- Check crank and cam sensors (DIS system).
HESITATION - COASTING
- Check fuel injectors.
- Check ignition and sensor wires for proper connection.
- Check throttle switch and connector.
- Check crank and cam sensors (DIS system).
- Check for gasoline in oil.
KNOCKING
- Check ignition timing.
- Check EGR valve operation.
- Check ignition and coil circuit.
- Ensure spark plugs fire.
- Check knock sensor (if applicable).
- Check throttle position sensor and connector.
- Check engine speed sensor.
- Check MAP sensor.
ENGINE MISFIRE - ALL CONDITIONS
- Check fuel injectors.
- Check ignition and sensor wires for proper connection.
- Check ignition and coil circuit.
- Check for gasoline in oil.
- Check intake and exhaust system.
- Check throttle position sensor and connector.
- Check for vacuum leaks.
- Check EGR valve operation.
- Check engine speed sensor.
- Check MAP sensor.
INSUFFICIENT ENGINE POWER
- Check fuel injectors.
- Ensure fuel pressure is correct.
- Check airflow sensor.
- Check for restricted exhaust.
- Check coolant temperature sensor.
- Check throttle position sensor and connector.
- Check ignition and coil circuit.
- Check MAP sensor.
- Check engine speed sensor.
- Check intake and exhaust system.
POOR FUEL ECONOMY
- Check for leaky fuel injectors.
- Ensure spark plugs are not fouled.
- Check for faulty oxygen sensor.
- Check throttle switch and connector.
- Check for poor wire connections and fouled spark plugs.
- Check engine speed sensor.
- Check for contaminated fuel.
- Check for gasoline in oil.
- Check MAP sensor.
EXCESSIVE HC & NOx
- Check for gasoline in oil.
- Check for leaky fuel injectors.
- Check for faulty oxygen sensor.
- Check ignition and sensor wires for poor connection.
- Check EGR valve operation.
- Check crank and cam sensors (DIS system).
- Check throttle position sensor and connector.
- Check for vacuum leaks.
Intermittent Simulation
To reproduce the conditions creating an intermittent fault, use the following methods
- Lightly vibrate component.
- Heat component.
- Wiggle or bend wiring harness.
- Spray component with water.
- Remove/apply vacuum source.
Monitor circuit/component voltage or resistance while simulating intermittent. If engine is running, monitor for self-diagnostic codes. Use test results to identify a faulty component or circuit.