13166493-13166488-13166513-13166518-13166523-13166498-13166503-13166508

COMPONENT LOCATION

GENERAL DESCRIPTION

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

If the ECM detects that engine speed variation indicates a misfire sufficient to cause three-way catalyst converter damage or emissions level to exceed standard value, the ECM sets DTC P0302. If the misfire rate is high enough to damage the catalyst, the MIL will flash to alert the vehicle operator.

DTC DETECTING CONDITION

Item		Detecting Condition	Possible Cause
DTC Strategy		● Calculation of engine roughness	● Faulty spark plugs, high-tension lead, or Ignition coil ● Incorrect valve timing ● Uneven compression ● Air leakage ● Improper Fuel pressure or dirty fuel. ● Blocked/Leaking injectors ● Leakage between cooling system and cylinder
Enable Conditions		● 170 ＜ Mass air flow (mg/rev.) ＜ 726 ● 512 ＜ Engine speed(RPM) ＜ 4500 ● 40 ＜ MAF gradient (mg/rev/Seg.) ＜ 400 ● 141 ＜ Throttle gradient (°TPS/sec.) ＜ 199 ● Coolant temperature ＞ 20℃ (-4℉) if Start temperature ＜ -7℃ (19.4℉) ● No rough road ● No relevant failure ● 11V ＜ Battery voltage ＜ 16V ● Fuel cut off not active
Threshold Value	Case1)	● Misfire = 12~54% within 200 rev.(Catalyst temperature ＞ 1000℃ (1832℉))
	Case2)	● Misfire = 1.3% within 1000 rev.
Diagnosis Time	Case1)	● 200 revolution or 3*200 revolution
	Case2)	● 1000 revolution or 4*1000 revolution
Mil On Condition	Case1)	● Immediate
	Case2)	● 2 Driving Cycles

SPECIFICATION

Temp.(℃)	Temp.(℉)	Primary ignition coil (Ω)	Secondary ignition coil(㏀)
20	68	0.58 ± 10%	8.8 ± 15%

MONITOR DTC STATUS

note

If any codes relating to injectors, HO2S, ECT(Engine Coolant Temperature)Sensor, Throttle Position sensor or Mass Air Flow Sensor are stored, do ALL REPAIRS associated with those codes before proceeding with this troubleshooting tree.

Connect scan tool and select "Diagnostic Trouble Codes(DTCs)" mode

Press F4(DTAL) to select DTC information from the DTCs menu

Confirm that "DTC Readiness Flag" indicates "Complete". If not, drive the vehicle within conditions noted in the freeze frame data or enable conditions

Read "DTC Status" parameter

Is parameter displayed "History(Not Present) fault"?

note

History (Not Present) fault : DTC occurred but has been cleared.

Present fault : DTC is occurring at present time.

▶ Fault is intermittent caused by poor contact in the sensor's and/or ECM's connector or was repaired and ECM memory was not cleared. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and then go to "Verification of Vehicle Repair" procedure.

▶ If any misfire DTCs related to companion cylinders{P0301(Cylinder1)＆P0304(Cylinder4), P0302(Cylinder2))＆P0303(Cylinder3)} are also stored, go to "Ignition System Inspection" procedure.If not, go to next step as below

VISUAL INSPECTION

Visually/physically inspect for the following conditions

Vacuum hoses in engine room for splits, kinks and improper installation

Positive crankcase ventilation valve for improper installation, damaged o-rings and malfunctioning .

Verify that the ECM ground connections are clean and properly tightened.

Check MAFS and ECTS for the following conditions:

The MAF signal displayed on the scantool should increase as engine speed increases

The engine coolant temperature displayed on the scantool should close to the actual coolant temperature.

Was a problem found in any of the above areas?

▶ Replace or repair as necessary and go to "Verification of Vehicle Repair" procedure

▶ Go to next step as below

TIMING INSPECTION

With ignition "OFF", set up an oscilloscope as follows :

Channel A (+): terminal 3 of the Crankshaft Position Sensor(CKPS), (-): ground

Channel B (+): terminal 3 of the Camshaft Position Sensor(CMPS), (-): ground

Start the engine and check for signal waveform whether synchronize with camshaft sensor or not.

Is the signal waveform normal?

▶ Go to next step as below.

▶ Repair or readjust as necessary, if air gap of the CKPS is exceeds specification[0.3~1.7 mm(0.012~0.067 in)]. If OK, check that the crankshaft and camshaft are correctly aligned the matching marks of the pulleys. Repair or readjust as necessary and go to "Verification of Vehicle Repair" procedure.

IGINITION SYSTEM INSPECTION

Spark Plug Cable & Ignition Coil Inspection

(1)

Visually/physically inspect the spark plug cable and ignition coil related to the misfiring cylinder(s) for the following conditions

Damage, cracks, carbon and flashover

Poor connection or damaged harness

Connected to the incorrect cylinders at the ignition coil and spark plug

(2)

Measure the resistance of the spark plug cable related to the misfiring cylinder(s)

Specification : 5.6㏀/m ± 20% at 20℃(68℉)

(3)

Measure the resistance of the primary and secondary ignition coil related to the misfiring cylinder(s)

Specification :

Primary Ignition Coil Resistance : 0.58Ω ± 10% at 20℃(68℉)

Secondary Ignition Coil Resistance : 8.8㏀ ± 15% at 20℃(68℉)

(4)

Was a problem found in any of the above areas?

▶ Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure

▶ Go to next step as below

Spark Plug Inspection

(1)

Visually/physically inspect the spark plug related to the misfiring cylinder(s) for the following conditions

Damaged insulation, Worn electrodes, Oil or fuel fouled, Loose terminals and cracks

Check for electrode 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.

(2)

Was a problem found in any of the above areas?

▶ Replace or adjust as necessary and go to "Verification of Vehicle Repair" procedure

▶ Go to next step as below

FUEL SYSTEM INSPECTION

Fuel Line Pressure Inspection

(1)

Check the fuel for excessive water, alcohol, or other contaminants. Replace contaminated fuel as necessary.

(2)

Install a fuel pressure gage

(3)

Inspect fuel pressure with normal idle status

Specification : 338~348kPa(3.45~3.55kg/㎠)

(4)

Is fuel pressure within the specified value?

▶ Go to next step as below

▶ Inspect the suspected area. Refer to table as below. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure.

Condition	Possible Cause	Suspected Area
Fuel Pressure too low	Clogged fuel filter	Fuel filter
Fuel Pressure too low	Fuel leak on the fuel-pressure regulator that is assembled on fuel pump	Fuel Pump(Fuel Pressure Regulator)
Fuel Pressure too High	Sticking fuel pressure regulator	Fuel Pump(Fuel Pressure Regulator)

Fuel Pressure Hold Inspection

(1)

Stop the engine and check for a change in the fuel pressure gauge reading.

Specification : After engine stops, the gauge reading should hold for minimum 5 minutes

(2)

Is fuel pressure within the specified value?

▶ Go to next step as below

▶ Inspect the suspected area. Refer to table as below. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure.

Condition	Possible Cause	Suspected Area
Fuel pressure drops slowly	Injector leak	Injector
Fuel pressure drops immediately	Stuck open in check valve of the fuel pump	Fuel pump

ENGINE COMPRESSION TEST

Warm up the engine to normal operating temperature. Verify the battery must be at or near full charge.

With ignition "OFF", disconnect the ignition coil connectors and the spark plug cables

Install compression pressure gauge to the spark plug hole.

With wide open throttle by hand, cranking the engine and record the compression readings from all of the cylinders

Specification :

Compression pressure : 1,283kPa (13.0kgf/cm², 185psi)

Minimum pressure : 1,135kPa (11.5kgf/cm², 164psi)

Difference between each cylinder : 100kPa (1.0kgf/cm², 15psi) or less

Is compression pressure within the specified value?

▶ Verify if the engine has excessive coolant consumption. If yes, check for damaged inlet water passage, engine block, cylinder head or head gasket. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure

▶ If the cylinder compression in 1 or more cylinders is low, pour a small amount of engine oil into the cylinder through the spark plug hole and repeat compression test for cylinders with low compression pressure.

If adding oil helps the compression, it is likely that the piston rings and/or cylinder bore are worn or damaged.

If pressure stays low, a valve may be sticking or seating is improper, or there may be leakage past the gasket.

Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure

VERIFICATION OF VEHICLE REPAIR

After a repair, it is essential to verify that the fault has been corrected.

Connect scan tool and select "Diagnostic Trouble Codes(DTCs)" mode.

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.

Read "DTC Status" parameter.

Is parameter displayed "History(Not Present) fault"?

▶ System performing to specification at this time. Clear the DTC

▶ Go to the applicable troubleshooting procedure.