NO START (COLD ENGINE)
- Ensure battery is fully charged
- Check for contaminated fuel
- Check spark plugs
- Check fuel pump fuse(s)
- Check in-line fuse to control unit (if applicable)
- Ensure ignition timing and fuel pressure are correct
- Check fuel injectors
- Ensure timing belt is not broken (if applicable)
- Ensure ignition coil resistance is correct
- Ensure rotor, distributor and spark plug wires are okay
- Check ignition control unit
- Check coolant temperature sensor and connector
- Check throttle switch and connector (if applicable)
- Check engine speed sensor
- Check airflow sensor
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 engine speed sensor
- Check throttle switch and connector (if applicable)
STARTS BUT STALLS
- Check coolant temperature sensor
- Check ignition and sensor wires for proper connection
- Check fuel injectors
- Check throttle switch and connector (if applicable)
- Check engine speed sensor
HARD TO START (COLD ENGINE)
- Check spark plugs
- Check distributor (if applicable)
- Ensure fuel pressure is correct
- Check ignition timing
- Check throttle switch and connector (if applicable)
ERRATIC IDLE (WARM-UP)
- Check throttle switch and connection (if applicable)
- Check coolant temperature sensor and connection
- Check air temperature sensor (if applicable)
- 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 engine speed sensor
- Check throttle switch and connector (if applicable)
- Check MAP sensor (if applicable)
ENGINE SURGES
- Check ignition and fuel system
- Check for vacuum leaks
- Check EGR system
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
- Check ignition and coil circuit
- Check engine speed sensor
- 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 switch and connector (if applicable)
- Check distributor (if applicable)
HESITATION ON ACCELERATION
- Check ignition and sensor wires for proper connection
- Check distributor cap for moisture or carbon tracking (if applicable)
- Ensure spark plug wires are okay
- Ensure spark plugs are not fouled
- Check MAP sensor (if applicable)
- Check throttle switch and connector (if applicable)
- Check ignition and coil circuit
- Check engine speed sensor
HESITATION WHEN COASTING
- Check fuel injectors
- Check ignition and sensor wires for proper connection
- Check throttle switch and connector
- Check engine speed sensor
- Check for gasoline in oil
KNOCKING
- Check ignition and coil circuit
- Check for defect in throttle body power system
- Check for restrictions at throttle body air inlet
- Check EGR system
- Ensure spark plugs fire
- Check knock sensor (if applicable)
- Check throttle switch and connector (if applicable)
- Check engine speed sensor
- Check MAP sensor (if applicable)
ENGINE MISFIRE ON 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 switch and connector (if applicable)
- Check for vacuum leaks
- Check engine speed sensor
- Check MAP sensor (if applicable)
INSUFFICIENT ENGINE POWER
- Check fuel injectors
- Check for air inlet restriction
- Ensure fuel pressure is correct
- Check airflow sensor
- Check for restricted exhaust
- Check coolant temperature sensor
- Check air temperature sensor (if applicable)
- Check throttle switch and connector (if applicable)
- Check ignition and coil circuit
- Check MAP sensor (if applicable)
- Check engine speed sensor
- Check intake and exhaust system
- Check EGR 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
- Check engine speed sensor
- Check for gasoline in oil
- Check MAP sensor (if applicable)
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 engine speed sensor
- Check throttle switch and connector (if applicable)
- 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.