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Home >> Mazda >> 2014 >> MX-5 Miata Club, Standard Trans >> Repair and Diagnosis >> Engine Performance >> System >> Symptom Troubleshooting [Engine Control System] >> No. 29 Spark Plug Condition

No. 29 Spark Plug Condition

29  SPARK PLUG CONDITION 
DESCRIPTION 
  • An incorrect spark plug condition.
POSSIBLE CAUSE 
NOTE:
  • Inspecting spark plugs condition can determine whether 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
  • Compression-Low compression
  • Clogging in intake/exhaust system
Grayish white with all plugs: 
  • 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 servicing the fuel system:
    • Fuel vapor is hazardous. It can easily ignite, causing serious injury and damage. Always keep sparks and flames away from fuel.
    • Fuel line spills and leakage are dangerous. Fuel can ignite and cause serious injuries or death and damage. Fuel can also irritate skin and eyes. To prevent this, always complete "BEFORE SERVICE PRECAUTION " and "AFTER SERVICE PRECAUTION ".
    CAUTION:
    • Disconnecting/connecting quick release connector without cleaning it may cause damage to fuel pipe and quick release connector. Always clean quick release connector joint area before disconnecting/connecting, and make sure that it is free of foreign material.
DIAGNOSTIC PROCEDURE

STEP INSPECTION RESULTS ACTION
1 Remove all spark plugs.
Inspect the spark plug condition.
Is the spark plug condition normal?		 Yes Symptom troubleshooting completed.
No 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.
2 Are the spark plug wet/covered with carbon by the engine oil? Yes Inspect all areas related to oil, working up and down.
No Go to the next step.
3 Inspect the spark plug for the following:
  • Cracked insulator
  • Heat range
  • Air gap
  • Worn electrode

Is the spark plug normal?		 Yes Go to the next step.
No Replace the spark plug.
(See SPARK PLUG REMOVAL/INSTALLATION ).
4 Inspect the compression pressure at suspected malfunctioning cylinder.
Is the compression pressure correct?
(See COMPRESSION INSPECTION ).		 Yes Go to the next step.
No Repair or replace the malfunctioning part according to the inspection results.
5 Install all spark plugs.
Perform the Spark Test at suspected malfunctioning cylinder.
(See ENGINE CONTROL SYSTEM OPERATION INSPECTION ).
Is the strong blue spark visible?
(Compare with normal cylinder).		 Yes Go to the next step.
No Repair or replace the malfunctioning part according to the inspection results.
6 Install the fuel pressure gauge between fuel fitter and fuel distributor.
Turn the ignition switch to the ON position (Engine off).
Turn to on the fuel pump using the M-MDS simulation function "FP".
Is the fuel line pressure correct when the fuel pump is turned to on?
(See FUEL LINE PRESSURE INSPECTION ).		 Yes Inspect the fuel injector for the following:
  • Open or short circuit in injector
  • Leakage
  • Injection volume
No Zero or low: 
  • Inspect the fuel pump relay and fuel pump circuit.
  • Inspect the fuel line for clogging.
  • If there is no malfunction, replace the fuel pump unit.

    (See FUEL PUMP UNIT REMOVAL/INSTALLATION ).


High: 
7 Inspect the spark plug for the following.
  • Heat range
  • Air gap

Is the spark plug normal?		 Yes Go to the next step.
No Replace the spark plug.
(See SPARK PLUG REMOVAL/INSTALLATION ).
8 Perform the Fuel Injector Operation Inspection.
(See ENGINE CONTROL SYSTEM OPERATION INSPECTION ).
Is the strong blue spark visible at each cylinder?		 Yes Go to the next step.
No Repair or replace the malfunctioning part according to fuel injector operation inspection result.
9 Is the air cleaner element free of clogging? Yes Go to the next step.
No Replace the air cleaner element.
10 Perform the Spark Test.
(See ENGINE CONTROL SYSTEM OPERATION INSPECTION ).
Is the strong blue spark visible at each cylinder?		 Yes Go to the next step.
No Repair or replace the malfunctioning part according to the inspection results.
11 Install the fuel pressure gauge between the fuel filter and fuel distributor.
Turn the ignition switch to the ON position (Engine off).
Turn to on the fuel pump using the M-MDS simulation function "FP".
Is the fuel line pressure correct when the fuel pump is turned to on?
(See FUEL LINE PRESSURE INSPECTION ).		 Yes Go to the next step.
No Zero or low: 
  • Inspect the fuel pump relay and fuel pump circuit.
  • Inspect the fuel line for clogging.
  • If there is no malfunction, replace the fuel pump unit.

    (See FUEL PUMP UNIT REMOVAL/INSTALLATION ).


High: 
12 Inspect the following PIDs:
  • ECT
  • O2S11 (When engine can be started).
  • O2S12 (When engine can be started).
  • MAF

Are the PIDs normal?
(See PCM INSPECTION ).		 Yes Go to the next step.
No Repair or replace the malfunctioning part according to the inspection results.
13 Perform the Purge Control System Inspection when engine can be started.
(See ENGINE CONTROL SYSTEM OPERATION INSPECTION ).
Is the purge control correct?		 Yes Go to the next step.
No Repair or replace the malfunctioning part according to the inspection results.
14 Perform the compression inspection.
(See COMPRESSION INSPECTION ).
Is the compression correct?		 Yes Visually inspect for deformed exhaust system part.
No Repair or replace the malfunctioning part according to the inspection results.
15 When the engine cannot be started, inspect the intake-air system for air leakage.
When the engine can be started, perform intake manifold vacuum inspection.
Is the air sucked in from intake-air system?		 Yes Repair or replace the malfunctioning part according to the inspection results.
No Go to the next step.
16 Install the fuel pressure gauge between the fuel filter and the fuel distributor.
Turn the ignition switch to the ON position (Engine off).
Turn to on the fuel pump using the M-MDS simulation function "FP".
Is the fuel line pressure correct when the fuel pump is turned to on?
(See FUEL LINE PRESSURE INSPECTION ).		 Yes Inspect the following PIDs:

Inspect the PCM ground condition.
No Zero or low: 
  • Inspect the fuel pump relay and fuel pump circuit.
  • Inspect the fuel line for clogging.
  • If there is no malfunction, replace the fuel pump unit.

    (See FUEL PUMP UNIT REMOVAL/INSTALLATION ).


High: 
17
  • Verify test results.
    • If normal, return to diagnostic index to service any additional symptoms.

      (See SYMPTOM DIAGNOSTIC INDEX ).

    • If malfunction remains, inspect related Service Bulletins and/or On-line Repair Information and perform repair or diagnosis.
      • If vehicle is repaired, troubleshooting completed.
      • If vehicle is not repaired or additional diagnostic information is not available, replace the PCM.

        (See PCM REMOVAL/INSTALLATION ).
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