NO.29 SPARK PLUG CONDITION [MZI-3.7]

id0103d2803600

29 | SPARK PLUG CONDITION
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DESCRIPTION | • 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 • Erratic signal to PCM ― CHT sensor 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 • Clogging in intake/exhaust system Grayish white with all plugs: • Air/fuel mixture—Too lean, insufficient fuel line pressure • Erratic signal to PCM ― CHT sensor or related circuit malfunction ― MAF sensor or related circuit malfunction ― A/F sensor or related circuit malfunction ― HO2S or related circuit malfunction 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” described in this manual. (See BEFORE SERVICE PRECAUTION [MZI-3.7].)(See AFTER SERVICE PRECAUTION [MZI-3.7].) 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
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1 | Remove all the spark plugs. (See SPARK PLUG REMOVAL/INSTALLATION [MZI-3.7].) Inspect the spark plug condition. (See SPARK PLUG INSPECTION [MZI-3.7].) 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 [MZI-3.7].)
4 | Inspect the compression pressure at suspected malfunctioning cylinder. (See COMPRESSION INSPECTION [MZI-3.7].) Is the compression pressure normal? | 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 [MZI-3.7].) Is 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 | Inspect the fuel line pressure. (See FUEL LINE PRESSURE INSPECTION [MZI-3.7].) Is the fuel line pressure correct? | Yes | Inspect fuel injector for the following: • Open or short circuit in injector • Leakage • Injection volume Repair or replace the malfunctioning part according to the inspection results.
No | Zero or low: • Inspect the following: ― Fuel pump relay ― Fuel pump circuit ― Fuel line for clogging • If there is no malfunction, replace the fuel pump unit. (Fuel pump or pressure regulator malfunction) (See FUEL PUMP UNIT REMOVAL/INSTALLATION [MZI-3.7].) High: • Replace the fuel pump unit. (Pressure regulator malfunction) (See FUEL PUMP UNIT REMOVAL/INSTALLATION [MZI-3.7].)
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 [MZI-3.7].)
8 | Remove the suspected fuel injector. (See FUEL INJECTOR REMOVAL/INSTALLATION [MZI-3.7].) Inspect the following: • Resistance • Fuel injection volume (See FUEL INJECTOR INSPECTION [MZI-3.7].) Are all above items normal? | Yes | Inspect for open circuit in wiring harness between fuel injector terminal A and PCM at the following terminals: • For No.1 cylinder: 2BQ • For No.2 cylinder: 2BC • For No.3 cylinder: 2AY • For No.4 cylinder: 2BG • For No.5 cylinder: 2BL • For No.6 cylinder: 2BI Repair or replace suspected wiring harness and connector.
No | Replace the fuel injector. (See FUEL INJECTOR REMOVAL/INSTALLATION [MZI-3.7].)
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 [MZI-3.7].) Is 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 | Inspect the fuel line pressure. (See FUEL LINE PRESSURE INSPECTION [MZI-3.7].) Is the fuel line pressure correct? | Yes | Go to the next step.
No | Zero or low: • Inspect the following: ― Fuel pump relay ― Fuel pump circuit ― Fuel line for clogging • If there is no malfunction, replace the fuel pump unit. (Fuel pump or pressure regulator malfunction) (See FUEL PUMP UNIT REMOVAL/INSTALLATION [MZI-3.7].) High: • Replace the fuel pump unit. (Pressure regulator malfunction) (See FUEL PUMP UNIT REMOVAL/INSTALLATION [MZI-3.7].)
12 | Access and monitor the following PCM PIDs using the M-MDS: (See ON-BOARD DIAGNOSTIC TEST [MZI-3.7].) • ECT • O2S11 (When engine can be started.) • O2S12 (When engine can be started.) • O2S21 (When engine can be started.) • O2S22 (When engine can be started.) • MAF Are all PIDs normal? (See PCM INSPECTION [MZI-3.7].) | Yes | Go to the next step.
No | Repair or replace the malfunctioning part according to the inspection results.
13 | Perform the purge control inspection. (When engine can be started.) (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [MZI-3.7].) Is the purge control normal? | Yes | Go to the next step.
No | Repair or replace the malfunctioning part according to the inspection results.
14 | Inspect the compression pressure. (See COMPRESSION INSPECTION [MZI-3.7].) Is the compression pressure normal? | Yes | Visually inspect for deformed exhaust system part. Repair or replace the malfunctioning part according to the inspection results.
No | Repair or replace the malfunctioning part according to the inspection results.
15 | Inspect the following: • Intake-air system for air leakage (When the engine cannot be started) • Intake manifold vacuum (When the engine can be started) Is 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 | Inspect the fuel line pressure. (See FUEL LINE PRESSURE INSPECTION [MZI-3.7].) Is the fuel line pressure correct? | Yes | Access and monitor the following PCM PIDs using the M-MDS: (See ON-BOARD DIAGNOSTIC TEST [MZI-3.7].) • ECT • O2S11 • O2S12 • O2S21 • O2S22 • MAF Repair or replace the malfunctioning part according to the inspection results. (See PCM INSPECTION [MZI-3.7].)
No | Zero or low: • Inspect the following: ― Fuel pump relay ― Fuel pump circuit ― Fuel line for clogging • If there is no malfunction, replace the fuel pump unit. (Fuel pump or pressure regulator malfunction) (See FUEL PUMP UNIT REMOVAL/INSTALLATION [MZI-3.7].) High: • Replace the fuel pump unit. (Pressure regulator malfunction) (See FUEL PUMP UNIT REMOVAL/INSTALLATION [MZI-3.7].)
17 | • Verify test results. ― If normal, return to diagnostic index to service any additional symptoms. (See SYMPTOM DIAGNOSTIC INDEX [MZI-3.7].) ― If malfunction remains, inspect related Service 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 [MZI-3.7].)