The Misfire monitor diagnostic is based on crankshaft rotation velocity variation. The ECM determines crankshaft rotational velocity using the crankshaft position sensor and camshaft position sensor. When a cylinder misfires the crankshaft slows down momentarily. By monitoring the crankshaft and camshaft position sensor signals, the ECM can calculate when a misfire occurs. For a non-catalyst damaging misfire, the diagnostic will be required to report a misfire present within 1000-3200 engine revolutions. For catalyst damaging misfire, the diagnostic will respond to monitor 200 engine revolutions. Rough roads may cause false misfire detection. The rough road(acceleration)sensor consists of a piezoelectric vibration pick up which detects vertical acceleration of the vehicle. The sensor signal is used by the ECM to determine the degree of vertical movement of the car, for example, on a bumpy road. Since this may also cause uneven engine running, the ECM uses the signal to distinguish the phenomenon from actual misfiring.
DTC DESCRIPTION
The misfire diagnostic 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. PCM sets this DTC. In case that misfire affects Catalyst damage, MIL(Malfunction Indication 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.
Especially, if injector connector / Ignition coil is disconnected for more than 46 sec., PCM sets DTC relating to misfire and conducts the fuel-cut to protect the catalyst.
DTC DETECTING CONDITION
Item
Detecting Condition
Possible Cause
DTC Strategy
●
Determine if a multiple cylinder misfire or a cylinder specific misfireis occurring by monitoring crankshaft acceleration.
●
Faulty Spark plugs
●
Faulty Spark plug cables
●
Air Leakage
●
Belt deflection and Air gap of CKPS
●
Incorrect timing
●
Faulty injector
●
Improper fuel pressure
●
Improper enginecompression
Enable condition
●
No disabling faults present / no disabiling Active Faults
The ECT indicates an engine temperaturebetween -6℃(20℉) and 120℃(248℉)
Threshold value
Case 1
●
Individual cylinder misfire detection
Case 2
●
Emissions damaging - 18 times in 600 ignitions(In case that the misfire affects more than 1.5 timesthan 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
●
2 driving cycles
MONITOR DTC STATUS
1.
Check DTC Status
(1)
Connect scantool to Data Link Connector(DLC).
(2)
IG "ON".
(3)
Select "Diagnostic Trouble Codes(DTCs)" mode, and then Press F4(DTAL) to check DTC's information from the DTCs menu
(4)
Read "DTC Status" parameter.
(5)
Is parameter displayed "Present fault"?
▶ Go to "System inspection" procedure.
▶ Although the misfire does not occur when the vehicle is brought to workshop, misfire can be reproducedwhen the condition is met. Drive the vehicle according to the freeze frame data in order to satisfy thecondition.
SYSTEM INSPECTION
1.
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?
▶ Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure
▶ Go to "Check Air Leakage " as below
2.
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?
▶ Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure
▶ Go to "Check for air leakage in Positive Crankcase Ventilation Valve(PCV)
3.
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 ?
▶ Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure
▶ Go to "Check Compression pressure" as below
4.
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
(6)
Is compression pressure for each cylinder displayed within specifications ?
Specification : 1323kPa(13.5 kg/cm²,192 psi)
▶ Go to "Check Timing " as below
▶ 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 is leaking from the gasket. Repair as necessary and go to "Verification of Vehicle Repair" procedure
5.
Check Timing
(1)
Ignition "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
(3)
Are all timing marks alligned correctly ?
▶ Go to "Check Fuel Pressure Test" as below
▶ 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
6.
Check fuel pressure
note
-
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 ventilationto 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 systempressure before disconnecting any fuel line to reduce the chance of presonal injury orfire 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.
Is the measured fuel pressure within specifications ?
▶ Substitute with a known - good PCM and check for proper operation.
▶ If the problem is corrected, replace PCM and go to "Verification of Vehicle Repair" procedure.
▶ Repair or replace according to the below table. And then, go to " Verification of VehicleRepair"procedure.
Condition
Possible Cause
Fuel Pressure is too low
Fuel filter,fuel pressure regulator, in-tank fuel hose or the fuel pump
Fuel Pressure is too high
Fuel pressure regulator, hose or pipe
VERIFICATION OF VEHICLE REPAIR
1.
Connect scan tool and select "Diagnostic Trouble Codes(DTCs)" mode
2.
Press F4(DTAL) and confirm that "DTC Readiness Flag" indicates "Complete". If not, drive the vehicle within conditions noted in the freeze frame data or enable conditions
3.
Read "DTC Status" parameter
4.
Is parameter displayed "History(Not Present) fault"?
▶ System performing to specification at this time. Clear the DTC.
