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NO.28 SPARK PLUG CONDITION [SKYACTIV-G 2.0]

28

SPARK PLUG CONDITION

DESCRIPTION

  • Incorrect spark plug condition.

POSSIBLE CAUSE

NOTE:

  • Inspecting the spark plug conditions can determine whether a problem is related to a specific cylinder or possibly all cylinders.

Wet/carbon stuck on specific plug:

  • Spark—Weak, not visible

  • Air/fuel mixture—Excessive fuel injection volume

  • Compression—No compression, low compression

  • Malfunction spark plug

Grayish white with specific plug:

  • Air/fuel mixture—Insufficient fuel injection volume

  • Malfunction spark plug

Wet/carbon is stuck on all plugs:

  • Spark—Spark weak

  • Air/fuel mixture—Too rich, excessive fuel line pressure

  • Erratic signal to PCM

    • ECT sensor No.1 or related circuit malfunction

    • MAF sensor or related circuit malfunction

    • A/F sensor or related circuit malfunction

    • HO2S or related circuit malfunction

  • Compression—Low compression

  • Restriction in intake/exhaust system

Grayish white with all plugs:

  • Erratic signal to PCM

    • ECT sensor No.1 or related circuit malfunction

    • MAF sensor or related circuit malfunction

    • A/F sensor or related circuit malfunction

    • HO2S or related circuit malfunction

  • Air/fuel mixture—Too lean, insufficient fuel line pressure

WARNING:

  • The following troubleshooting flow chart contains the fuel system diagnosis and repair procedures. Read the following warnings before performing the fuel system services:

    • Fuel vapor is hazardous. It can easily ignite, causing serious injury and damage. Always keep sparks and flames away from fuel.

    • Highly pressurized fuel may spray out if the fuel line is cut. Due to the following dangers occurring with a fuel spray, always complete the “Fuel Line Safety Procedure” to prevent the fuel from spraying. (See BEFORE SERVICE PRECAUTION [SKYACTIV-G 2.0].)

      • Fuel may cause irritation if it comes in contact with skin and eyes.

      • If fuel ignites and causes a fire, it may lead to serious injury or death, and damage to property and facilities.

    • Fuel is highly flammable and dangerous. Fuel line spills and leakage can cause serious injury or death, and damage to equipment. Always refer to the “Quick Release Connector Removal/Installation (fuel system)” before performing the fuel hose installation, and execute the “Fuel Leakage Inspection” after installation. (See QUICK RELEASE CONNECTOR REMOVAL/INSTALLATION [SKYACTIV-G 2.0].) (See AFTER SERVICE PRECAUTION [SKYACTIV-G 2.0].)

CAUTION:

  • Disconnecting/connecting the quick release connector without cleaning it may cause damage to the fuel pipe and the quick release connector. Always clean the quick release connector joint area before disconnecting/connecting, and make sure that it is free of foreign matter.

CAUTION:

  • Verify the malfunction symptom according to not only the PID value but also the symptom troubleshooting.

Related PIDs

Item (definition)

Unit/Condition

Definition

Condition/Specification (Reference)

ECT

°C, °F

Engine coolant temperature input from ECT sensor No.1

  • Displays ECT

V

ECT sensor No.1 voltage
    Ignition switched ON (engine off)

  • ECT is 92 °C {198 °F}: Approx. 0.65 V

    Idle (after warm up)

  • ECT is 93 °C {199 °F}: Approx. 0.64 V

    Racing (Engine speed is 2,000 rpm)

  • ECT is 92 °C {198 °F}: Approx. 0.66 V

    Racing (Engine speed is 4,000 rpm)

  • ECT is 93 °C {199 °F}: Approx. 0.64 V

MAF

g/Sec

Mass air flow input from MAF sensor

  • Displays MAF

V

MAF sensor voltage

  • Ignition switched ON (engine off) (MAF: 0.39 g/s {0.052 lb/min}): Approx. 0.72 V (ECT is 89 °C {192 °F})

  • Idle (after warm up) (MAF: 4.29 g/s {0.567 lb/min}): Approx. 1.15 V (ECT is 88 °C {190 °F})

  • Racing (engine speed is 2,000 rpm) (MAF: 4.32 g/s {0.571 lb/min}): Approx. 1.15 V (ECT is 89 °C {192 °F})

  • Racing (engine speed is 4,000 rpm) (MAF: 12.71 g/s {1.681 lb/min}): Approx. 1.66 V (ECT is 89 °C {192 °F})

O2S11

µA

A/F sensor current

  • Idle (after warm up): −59 µA (ECT is 92 °C {198 °F})

  • Deceleration fuel cut (accelerator pedal released from engine speed of 4,000 rpm or more): Approx. 3.48 mA (ECT is 92 °C {198 °F})

O2S12

V

HO2S voltage

  • Idle (after warm up): 0—1.0 V (ECT is 91 °C {196 °F})

  • Deceleration fuel cut (accelerator pedal released from engine speed of 4,000 rpm or more): Approx. 0 V (ECT is 92 °C {198 °F})

RPM

RPM

Engine speed

  • Displays engine speed

VSS

KPH, MPH

Vehicle speed

  • Displays vehicle speed
Diagnostic Procedure

STEP

INSPECTION

RESULTS

ACTION

1

 VERIFY SPARK PLUG CONDITION

Yes

Specific plug is wet or covered with carbon:

  • Go to the next step.

Specific plug looks grayish white:

  • Go to Step 7.

All plugs are wet or covered with carbon:

  • Go to Step 9.

All plugs look grayish white:

  • Go to Step 15.

No

Symptom troubleshooting completed.

2

 DETERMINE IF MALFUNCTION CAUSE IS ENGINE OIL LOSS OR OTHER

  • Are the spark plugs wet/covered with carbon from the engine oil?

Yes

Inspect all areas related to oil, working up and down.

Repair or replace the malfunctioning part according to the inspection results.

No

Go to the next step.

3

 INSPECT SPARK PLUG

  • Inspect the spark plugs for the following:

    • Air gap

    • Cracked insulator

    • Heat range

    • Worn electrode

  • Is there any malfunction?

Yes

Replace the spark plug.

(See SPARK PLUG REMOVAL/INSTALLATION [SKYACTIV-G 2.0].)

No

Go to the next step.

4

 INSPECT ENGINE COMPRESSION

Yes

Go to the next step.

No

Repair or replace the malfunctioning part according to the inspection results.

5

 INSPECT IGNITION SYSTEM OPERATION

Yes

Go to the next step.

No

Repair or replace the malfunctioning part according to the inspection results.

6

 INSPECT FUEL LINE PRESSURE
    Specification:

  • 425—505 kPa {4.34—5.14 kgf/cm2, 61.7—73.2 psi}

Yes

Inspect the fuel injector for the following:

  • Injection volume

  • Leakage

  • Open or short circuit in fuel injector

Repair or replace the malfunctioning part according to the inspection results.

No

Zero or low:

  • Inspect the fuel pump relay and the fuel pump circuit.

    (See RELAY INSPECTION.)

  • Inspect the fuel line for restriction.

    • If there is any malfunction:

      • Repair or replace the malfunctioning part according to the inspection results.

    • If there is no malfunction:

High:

7

 INSPECT SPARK PLUG

  • Inspect the spark plug for the following:

    • Air gap

    • Heat range

  • Is there any malfunction?

Yes

Replace the spark plug.

(See SPARK PLUG REMOVAL/INSTALLATION [SKYACTIV-G 2.0].)

No

Go to the next step.

8

 INSPECT FUEL INJECTOR OPERATION

Yes

Go to the next step.

No

Repair or replace the malfunctioning part according to the inspection results.

9

 INSPECT AIR CLEANER ELEMENT

  • Is the air cleaner element clean?

Yes

Go to the next step.

No

Replace the air cleaner element.

10

 VERIFY CURRENT INPUT SIGNAL STATUS

Yes

Go to the next step.

No

ECT PID is not as specified:

MAF PID is not as specified:

O2S11 PID is not as specified:

O2S12 PID is not as specified:

Repair or replace the malfunctioning part according to the inspection results.

11

 INSPECT PURGE CONTROL SYSTEM OPERATION

Yes

Repair or replace the malfunctioning part according to the inspection results.

No

Go to the next step.

12

 INSPECT IGNITION SYSTEM OPERATION

Yes

Go to the next step.

No

Repair or replace the malfunctioning part according to the inspection results.

13

 INSPECT ENGINE COMPRESSION

Yes

Go to the next step.

No

Repair or replace the malfunctioning part according to the inspection results.

14

 INSPECT FUEL LINE PRESSURE
    Specification:

  • 425—505 kPa {4.34—5.14 kgf/cm2, 61.7—73.2 psi}

Yes

Visually inspect for deformed exhaust system parts.

Repair or replace the malfunctioning part according to the inspection results.

No

Zero or low:

  • Inspect the fuel pump relay and the fuel pump circuit.

    (See RELAY INSPECTION.)

  • Inspect the fuel line for restriction.

    • If there is any malfunction:

      • Repair or replace the malfunctioning part according to the inspection results.

    • If there is no malfunction:

High:

15

 VERIFY CURRENT INPUT SIGNAL STATUS

Yes

Go to the next step.

No

ECT PID is not as specified:

MAF PID is not as specified:

O2S11 PID is not as specified:

O2S12 PID is not as specified:

Repair or replace the malfunctioning part according to the inspection results.

16

 INSPECT INTAKE-AIR SYSTEM FOR AIR SUCTION

Yes

Repair or replace the malfunctioning part according to the inspection results.

No

Go to the next step.

17

 INSPECT FUEL LINE PRESSURE
    Specification:

  • 425—505 kPa {4.34—5.14 kgf/cm2, 61.7—73.2 psi}

Yes

Inspect the PCM ground condition.

Repair or replace the malfunctioning part according to the inspection results.

No

Zero or low:

  • Inspect the fuel pump relay and the fuel pump circuit.

    (See RELAY INSPECTION.)

  • Inspect the fuel line for restriction.

    • If there is any malfunction:

      • Repair or replace the malfunctioning part according to the inspection results.

    • If there is no malfunction:

High:

18

Verify the test results.

  • If normal, return to the diagnostic index to service any additional symptoms.

    (See SYMPTOM DIAGNOSTIC INDEX [SKYACTIV-G 2.0].)

  • If the malfunction remains, inspect the related Service Bulletins and/or On-line Repair Information and perform repair or diagnosis.

    • If the vehicle is repaired, troubleshooting is completed.

    • If the vehicle is not repaired or additional diagnostic information is not available, reprogram the PCM if a later calibration is available. Retest.
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Free to use workshop manual for your 2015+ Mk4 'ND' Mazda MX-5

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