NO.28 SPARK PLUG CONDITION [LF, L3]

id0103008045b2

28

SPARK PLUG CONDITION

DESCRIPTION

Incorrect spark plug condition

POSSIBLE CAUSE

Note
• Inspecting spark plugs condition can determine whether problem is related to a specific cylinder 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
• Faulty spark plug
Grayish white with specific plug:
• Air/fuel mixture-Insufficient fuel injection volume
• Faulty spark plug
Wet/carbon is stuck on all plugs:
• Spark-Spark weak
• Air/fuel mixture-Too rich
• Compression-Low compression
• Clogging in intake/exhaust system
• Improper adjustment of variable resister (Leaded gasoline model)
Grayish white with all plugs:
• Air/fuel mixture-Too lean
• Improper adjustment of variable resister (Leaded gasoline model)
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.
• 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 REPAIR PROCEDURE" and "AFTER REPAIR PROCEDURE" described in this manual.
(See BEFORE REPAIR PROCEDURE [LF, L3].)
(See AFTER REPAIR PROCEDURE [LF, L3].)
Caution
• Disconnecting/connecting the quick release connector without cleaning it may possibly 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 material.

Diagnostic procedure

STEP

INSPECTION

RESULTS

ACTION

1
Remove all the spark plugs.
Inspect the spark plugs.
Are the spark plugs 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 the 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 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.
4
Inspect the compression pressure at the suspected faulty cylinder.
Is the compression pressure correct?
Yes
Go to the next step.
No
Repair or replace the malfunctioning parts.
5
Install all spark plugs.
Carry out a spark test at the suspected faulty cylinder.
Is a strong blue spark visible?
(Compare with normal cylinder.)
Yes
Go to the next step.
No
Repair or replace the malfunctioning parts.
6
Carry out the fuel line pressure inspection.
Is the fuel line pressure correct?
Yes
Inspect the fuel injector for the following:
• Open or short in injector
• Leakage
• Injection volume
No

Zero or low:

Inspect the fuel pump circuit.
Inspect for fuel pump relief valve open.
Inspect for fuel leakage inside the pressure regulator.
Inspect for a clogged main fuel line.

High:

Inspect the pressure regulator for cause of the high pressure.
Inspect for a clogged fuel return line.
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.
8
Remove the suspected fuel injector.
Inspect the following:
• Resistance
• Fuel injection volume
Are all above items normal?
Yes
Inspect for an open circuit between the suspected fuel injector connector terminal and the PCM connector and the following terminals:

• For #1 or #4 cylinder: 1A

• For #2 or #3 cylinder: 1B

No
Replace the fuel injector.
9
Is the air cleaner element free of restrictions?
Yes
Go to the next step.
No
Replace the air cleaner element.
10
Carry out a spark test.
Is a strong blue spark visible at each cylinder?
Yes
Go to the next step.
No
Repair or replace the malfunctioning parts.
11
Carry out the fuel line pressure inspection.
Is the fuel line pressure correct?
Yes
Go to the next step.
No

Zero or low:

Inspect for a clogged fuel line.
If normal, replace the fuel pump unit.

High:

Replace the fuel pump unit.
12
Inspect the following PIDs:
• ECT
• O2S11 (When the engine can be started) (Unleaded gasoline model)
• MAF
Are all the PIDs normal?
Yes
Go to the next step.
No
Repair or replace the malfunctioning parts.
13
Carry out the purge control inspection.
(When engine can be started)
Is the purge control correct?
Yes
Go to the next step.
No
Repair or replace the malfunctioning parts.
14
Carry out the compression inspection.
Is the compression correct?
Yes
Inspect for clogging in the exhaust system.
No
Repair or replace the malfunctioning parts.
15
When the engine cannot be started, inspect intake-air system for air leakage.
When the engine can be started, carry out the intake manifold vacuum inspection.
Is air sucked in from the intake-air system?
Yes
Repair or replace the malfunctioning part.
No
Go to the next step.
16
Carry out the fuel line pressure inspection.
Is the fuel line pressure correct?
Yes
Inspect the following PIDs:
• ECT
• O2S11 (Unleaded gasoline model)
• MAF
(See PCM INSPECTION [LF, L3].)
Inspect the PCM ground condition.
If normal, inspect the variable resister adjustment. (Leaded gasoline model)
No

Zero or low:

Inspect for a clogged fuel line.
If normal, replace the fuel pump unit.

High:

Replace the fuel pump unit.
17
Verify the test results.
• If normal, return to the diagnostic index to service any additional symptoms.
• If the malfunction remains, replace or reprogram the PCM.