P0306 Cylinder 6 Misfire Detected

/ Engine DTCs / By
GENERAL DESCRIPTION
Misfires can be caused by lack of combustion in a cylinder due to absence of spark, poor fuel metering, poor compression, or many other causes. Even a small number of misfires may result in excessive exhaust emissions due to the unburned fuel mixture. Increased misfire rates will cause damage to the catalytic converter. The ECM monitors the crankshaft speed variation to determine if misfires occur. The ECM identifies the specific cylinder in which the misfire has occurred and counts individual misfire events by monitoring changes in the crankshaft rotation for each cylinder. A random misfire indicates two or more cylinders are misfiring.
DTC DESCRIPTION
The ECM measures reference event times and calculates the positive and negative acceleration of the crank wheel to detrmine whether a misfire has occurred.
When the rate of misfire exceeds a threshold where the catalyst reaches a temperature where permanent damage can ocur, to the point that tail pipe emissions reach 1.5 times the tailpipe standard or where a cylinder misfire cause a loss of torque produced from that cylinder. ECM sets this DTC. In case that misfire affects Catalyst damage, MIL(Malfunction Indicatin Lamp) will be illuminating and blinking at 1HZ frequency. However, In case of Indivisual and Emission damaging misfire, MIL will be turned on when the malfunction is detected.
DTC DETECTING CONDITION
 
ItemDetecting ConditionPossible Cause
DTC Strategy
Determine if a multiple cylinder misfire or a cylinder specific misfire is occurring by monitoring crankshaft acceleration.
1.
Faulty Spark plugs
2.
Faulty Spark plug cables
3.
Air Leakage
4.
Belt deflection and Air gap of CKPS
5.
Incorrect timing
6.
Faulty injector
7.
Improper fuel pressure
8.
Improper engine compression
Enable Conditions

No disabling faults present / no disabiling Active Faults

P0340 / P0341 / P0118 / P0117 / P0115 / P0336 / P0335 / P1295 / P0103 / P0102 / 0108 / P0107 / P0106 / P0501
Engine speed between 550 and 5800 RPM
System voltage between 9 and 18 volts
The ECT indicates an engine temperature between -6°C(20°F) and 120°C(248°F)
Threshold valueCase 1
Individual cylinder misfire detection
Case 2
Emissions damaging – 18 times in 600 ignitions
(In case that the misfire affects more than 1.5 times than FTP emissins)
Case 3
Catalyst damaging – 95 times in 600 ignitions at idle
( It is going to be changeable according to the load or the temperature which is not in the range where it does not melt catalyst)
Diagnosis Time
Continuous
MIL On Condition
3 Driving Cycles

 

SIGNAL WAVEFORM & DATA

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Fig.1) Normal data of misfire counter at idle.

Fig.2) Abnormal data of misfire counter when cylinder 4 injector open.

MONITOR GDS DATA
1.
Connect GDS to Data Link Connector(DLC).
2.
IG “ON”.
3.
Select “DTC” button, and then Press “DTC Status” to check DTC’s information from the DTCs menu.
4.
Read “DTC Status” parameter.

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5.
Is parameter displayed “Present fault”?
 

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▶ Go to “System Inspection” procedure.

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▶ Although the misfire does not occur when the vehicle is brought to workshop, misfire can be reproduced when the condition is met. Drive the vehicle according to the freeze frame data in order to satisfy the condition.
SYSTEM INSPECTION
■ Misfire Inspection
1.
Check the cylinder where the misfire occurs after replacing the ignition coil of the cylinder where the misfire has occurred with the ignition coil of the other cylinder.
2.
Does the misfiring cylinder change?
 

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▶ Go to “Ignition coil waveform inspection” procedure.

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▶ Repair as necessary except for the ignition coils and go to “Check Air Leakage” procedure.
■ Ignition coil waveform inspection
1.
Ignition “ON” and engine “ON”.
2.
Measure the voltage between control terminal of ignition soil harness connector and chassis ground.
 Refer to Fig.1

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Fig.1) Engine Idle after Warm Up
Spark retention time – Approx. 1.2ms
CH. A – Ignition Max 31V
3.
Is the measured waveform within specification?
 

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▶ Repair as necessary except for the ignition coils and go to “Check Air Leakage” procedure.

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▶ Go to “Check Spark Plug” procedure.
■ Check Spark Pulg
1.
Remove cylinder’s 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?
 

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▶ Repair or replace as necessary and go to “Verification of Vehicle Repair” procedure.

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▶ Go to “Check Air Leakage ” as below.
■ Check Air Leakage
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?
 

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▶ Repair or replace as necessary and go to “Verification of Vehicle Repair” procedure.

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▶ Go to “Check for air leakage in Positive Crankcase Ventilation Valve(PCV).
■ Check for air leakage in Positive Crankcase Ventilation Valve(PCV)
1.
Remove PCV valve from cylinder head cover by puling ventilation hose.
2.
With engine idling block PCV valve opening.
3.
Verify that vacuum is felt.
4.
Remove PCV valve.
5.
Blow through valve from prot “A” and verify that air comes out of prot “B”.
6.
Blow through valve from prot “B” and verifty that no air comes out of port “A”.
7.
Has a problem been found in any of the above areas?
 

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▶ Repair or replace as necessary and go to “Verification of Vehicle Repair” procedure.

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▶ Go to “Check Compression pressure” as below.
■ Check Compression pressure
1.
Warm up the engine to normal operating temperature.
2.
Disconnect the spark plug cables and remove the spark plugs.
3.
Crank the engine to remove any foreign material in the cylinders.
4.
Put compression pressure gauge into spark pulg hole.
5.
Crank the engine with widely opend throttle valve and check compression pressure at each cylinder.
 1323kPa(13.5 kg/cm²,192 psi)
6.
Is compression pressure for each cylinder displayed within specifications ?
 

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▶ Go to “Check Timing ” as below.

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▶ 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.
▶ If the compression remains the same, the cause is a burnt or defective valve seat, or pressure isleaking from the gasket. Repair as necessary and go to “Verification of Vehicle Repair” procedure
■ Check Timing
1.
IG “OFF”
2.
Monitor these signal waveforms from CAM and Crank shaft position Sensor are correctly aligned.
Reference : The 17th of CKP signal from missing tooth is aligned with high of CMP signal.

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3.
Are all timing marks aligned correctly ?
 

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▶ Go to “Check Fuel Pressure ” as below.

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▶ Check that Cam, Crank and Oil pump sprocket timing marks are correctly aligned. Repair or readjust as necessary and go to “Verification of Vehicle Repair” procedure.
■ Check fuel pressure
   
 
Be cautious that Fuel is explosive and an empty fuel tank can still contain explosive gases. When working on fuel system make sure to supply adequate ventilation to the work area. Do not smoke, and keep sparks and open flames away.
The fuel system remains under pressure when the engine is not running. Release fuel system pressure before disconnecting any fuel line to reduce the chance of personal injury or fire damage to vehicle components.
1.
IG “OFF” and disconnect Fuel Pump Relay in Junction Box.
2.
Start-up and wait until it stops itself.
3.
IG “OFF” and connect Fuel Pump Relay.
4.
Install the fuel pressure gauge to the delivery pipe with the fuel pressure gauge adaptor.
5.
Activate the fuel pump, and with fuel pressure applied, check that there is no fuel leakage from the pressure gauge or connection part.
6.
Measure the fuel pressure at idle.
 379.5kPa (3.87kgf/cm², 55.0psi)
7.
Is the measured fuel pressure within specifications ?
 

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▶ 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.
   
 
There is a memory reset function on GDS that can erase optional parts automatically detected and memorized by ECM. Before or after testing ECM on the vehicle, use this function to reuse the ECM on the others

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▶ Repair or replace according to the below table. And then, go to “Verification of Vehicle Repair” procedure.

 
ConditionPossible Cause
Fuel Pressure is too lowFuel filter, fuel pressure regulator, in-tank fuel hose or the fuel pump
Fuel Pressure is too highFuel pressure regulator, hose or pipe

 

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