System Inspection
P0300 Random/Multiple Cylinder Misfire Detected
Inspection/Repair - System Inspection
System Inspection
1. Spark plug check
(1) Remove cylinder spark plugs.
(2) Visually/physically inspect the following items:
- Damaged insulation, Worn electrodes, Oil or fuel fouled, Loose terminals and cracks
- Check for plug gap : 1.0 - 1.1 mm (0.039 - 0.043 in.)
- Check if the spark plug for the relevant cylinder is lighter in color than the other plugs.
(3) Has a problem been found in any of the above areas?
YES
1) Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure
NO
1) Go to "Compression pressure check" procedure.
2. Compression pressure check
(1) Warm up the engine to normal operating temperature.
(2) Disconnect the spark plug cables. And remove the spark plugs and fuel pump relay.
(3) Crank the engine to remove any foreign material in the cylinders.
(4) Put compression pressure gauge into spark plug hole.
(5) Check compression pressure at each cylinder.
A. Specification : Approx. 15 kg/cm2 (1.471MPa / 213.4 psi)
(6) Is compression pressure for each cylinder displayed within specifications?
YES
1) Go to "Ignition system check" procedure.
NO
1) Add a small amount of oil through the spark plug hole, and repeat above steps.
If the addition of oil causes the compression to rise, the cause is a worn or damaged piston ring or cylinder inner surface.
2) If the compression remains the same, the cause is a burnt or defective valve seat, or pressure is leaking from the gasket.
Repair as necessary and go to "Verification of Vehicle Repair" procedure.
3. Ignition system check
(1) Key "OFF".
(2) Disconnect Ignition coil connector.
(3) Do visual inspection.
> Check contamination or damage on ignition coil.
(4) Key "ON".
(5) Measure the voltage between terminal 2 of ignition coil #1, #2, #3, #4 harness connector and chassis ground.
A. Specification : Approx. B+
(6) Is the measured voltage within specifications?
YES
1) Go to "Timing mark check" procedure.
NO
1) Repair Open or Short to ground in power circuit, and go to "Verification of Vehicle Repair" procedure.
4. Timing mark check
(1) Key "OFF".
(2) Check the timing mark.
A. Specification :
(3) Is the timing mark normal?
YES
1) Go to "Air leakage check" procedure.
NO
1) Repair and go to "Verification of Vehicle Repair" procedure.
5. Air leakage check
(1) Visually/physically inspect the air leakage in intake/exhaust system as following items,
- Vacuum hoses for splits, kinks and improper connections.
- Throttle body gasket
- Gasket between intake manifold and cylinder head
- Seals between intake manifold and fuel injectors
- Exhaust system between HO2S and Three way catalyst for air leakage.
(2) Has a problem been found in any of the above areas?
YES
1) Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure
NO
1) Go to "PCV (Positive Crankcase Ventilation) valve check" procedure.
6. PCV (Positive Crankcase Ventilation) valve check
(1) Key "OFF".
(2) Disconnect PCV valve.
(3) Check PCV plunger movement.
(4) Is the movement of plunger normal?
YES
1) Go to "Injector check" procedure.
NO
1) Substitute with a known - good PCV valve and check for proper operation.
If the problem is corrected, replace PCV valve and go to "Verification of Vehicle Repair" procedure.
7. Injector check
(1) Key "OFF".
(2) Remove injectors.
(3) Check leakage or clog on injectors.
(4) Measure the resistance between terminal 1 and 2. (Component side)
A. Specification :
(5) Is the measured resistance within specification?
YES
1) Go to "Fuel line check" procedure.
NO
1) Substitute with a known - good injector and check for proper operation.
If the problem is corrected, replace injector and go to "Verification of Vehicle Repair" procedure.
8. Fuel line check
(1) Check clog, contamination and damage on fuel line.
- Splits, kinks and improper connections of fuel line pipe.
- Interference, damage and improper connections of vacuum hose on fuel line.
- Improper connection of connectors on fuel line.
(2) Is the fuel line normal?
YES
1) Go to "Fuel pressure check" procedure.
NO
1) Repair as necessary and go to "Verification of Vehicle Repair" procedure.
9. Fuel pressure check
(1) Key "OFF".
(2) Disconnect.
(3) Engine start and wait until engine stop. and then key "OFF".
(4) Install fuel pump relay.
(5) Connect fuel pressure gauge using the correct adaptor.
(6) Start the engine , and record fuel pressure.
A. Specification : Approx. 3.5 kg/cm2 (343.2 KPa / 50 psi)
(7) Is the fuel pressure normal?
YES
1) Substitute with a known - good ECM and check for proper operation.
If the problem is corrected, replace ECM and go to "Verification of Vehicle Repair" procedure.
CAUTION:
There is a memory reset function on scantool that can erase optional parts automatically detected and memorized by PCM.
Before or after testing PCM on the vehicle, use this function to reuse the PCM on the others
NO
1) Check clogging on the fuel filter.
Check the fuel supply and return line.
Repair as necessary and go to "Verification of vehicle Repair" procedure.