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Home >> Mazda >> 2002 >> Tribute LX, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 335 (Symptom Troubleshooting (Engine Control System L3)) >> No. 30 Spark Plug Condition >> Diagnostic procedure

Diagnostic procedure

WARNING: This page is about a different car, the 2005 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.
NO. 30 SPARK PLUG CONDITION DIAGNOSTIC PROCEDURE

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

Is spark plug normal?		 Yes Go to the next step.
No Replace spark plug.
4 Inspect compression pressure at suspected faulty cylinder.
Is compression pressure correct?
(See COMPRESSION INSPECTION .)		 Yes Go to the next step.
No Repair or replace malfunctioning parts.
5 Install all spark plugs.
Perform spark test at suspected faulty cylinder.
Is strong blue spark visible?
(Compare with normal cylinder		 Yes Go to the next step.
No Repair or replace malfunctioning parts.
6 Install fuel pressure gauge between fuel filter and fuel distributor.
Short check connector terminal F/P to body GND using a jumper wire.
Turn ignition switch to ON position (Engine off).
Is fuel line pressure correct with ignition switch at ON?
Fuel line pressure 
375-450 kPa {3.9-4.5 kgf/cm 2  , 55-65 psi} 		 Yes Inspect fuel injector for the following:
  • Open or short in injector
  • Leakage
  • Injection volume
No Zero or low: 
Inspect fuel pump relay and fuel pump circuit.
Inspect for clogged fuel line.
If okay, replace fuel pump unit.
High: 
Replace fuel pump unit.
7 Inspect spark plug for the following.
  • Heat range
  • Air gap

Is spark plug normal?		 Yes Go to the next step.
No Replace spark plug.
8 Remove suspected fuel injector.
Inspect the following:

Are all above items normal?		 Yes Inspect for open circuit between suspected fuel injector connector terminal and PCM connector at the following terminals:
  • For #1 cylinder: 76 (1) , 4Z (2) 
  • For #2 cylinder: 50 (1) , 4W (2) 
  • For #3 cylinder: 75 (1) , 4AD (2) 
  • For #4 cylinder: 49 (1) , 4AA (2) 
No Replace fuel injector.
9 Is air cleaner element free of restrictions? Yes Go to the next step.
No Replace air cleaner element.
10 Perform spark test.
Is strong blue spark visible at each cylinder		 Yes Go to the next step.
No Repair or replace malfunctioning parts.
11 Install fuel pressure gauge between fuel filter and fuel distributor.
Short check connector terminal F/P to body GND using a jumper wire.
Turn ignition switch to ON position (Engine off).
Is fuel line pressure correct with ignition switch at ON?
(See FUEL LINE PRESSURE INSPECTION .)
Fuel line pressure 
375-450 kPa {3.9-4.5 kgf/cm 2  , 55-65 psi} 		 Yes Go to the next step.
No Zero or low: 
Inspect fuel pump relay and fuel pump circuit.
Inspect for clogged fuel line.
If okay, replace fuel pump unit.
High: 
Replace fuel pump unit.
12 Inspect the following PIDs:
  • ECT
  • O2S11 (When engine can be started)
  • MAF

(See PCM INSPECTION .)
Are PIDs normal?		 Yes Go to the next step.
No Repair or replace malfunctioning parts.
13 Perform purge control inspection.
(When engine can be started)
(See PURGE CONTROL SYSTEM INSPECTION .)
Is purge control correct?		 Yes Go to the next step.
No Repair or replace malfunctioning parts.
14 Perform compression inspection.
Is compression correct?		 Yes Inspect for clogging in exhaust system.
No Repair or replace malfunctioning parts.
15 When engine cannot be started, inspect intake-air system for air leakage.
When engine can be started, perform intake manifold vacuum inspection.
Is air sucked in from intake-air system?		 Yes Repair or replace malfunctioning part.
No Go to the next step.
16 Install fuel pressure gauge between fuel filter and fuel distributor.
Short check connector terminal F/P to body GND using a jumper wire.
Turn ignition switch to ON position (Engine off).
Is fuel line pressure correct with ignition switch at ON?
(See FUEL LINE PRESSURE INSPECTION .)
Fuel line pressure 
375-450 kPa {3.9-4.5 kgf/cm 2  , 55-65 psi} 		 Yes Inspect the following PIDs:
  • ECT
  • O2S11
  • MAF

(See PCM INSPECTION .)
Inspect PCM GND condition.
No Zero or low: 
Inspect fuel pump relay and fuel pump circuit.
Inspect for clogged fuel line.
If okay, replace fuel pump unit.
High: 
Replace fuel pump unit.
17 Verify test results.
  • If okay, return to diagnostic index to service any additional symptoms.
  • 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, reprogram PCM if later calibration is available. Retest.
(1) California emission regulation applicable ATX model
(2) Except for California emission regulation applicable ATX model
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