Mazda 6 2002, Workshop Manual

Page: 355 / 1248

TROUBLESHOOTING
F–225
F
NO.28 SPARK PLUG CONDITION
A6E398018881W30
Diagnostic procedure
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
Grayish white with all plugs:
•
Air/fuel mixture—Too lean
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
F–17 BEFORE REPAIR PROCEDURE .)
(See F–17 AFTER REPAIR PROCEDURE .)
Caution
•
Disconnecting/connecting quick release connector without cleaning it may possibly 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.
STEP INSPECTION RESULTS ACTION
1 Remove all spark plugs.
Inspect spark plug condition.
Is spark plug condition okay? Yes Troubleshooting completed.
No Specific plug is wet or covered with carbon:
Go to 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 next step.
3 Inspect spark plug for following:
•
Cracked insulator
•
Heat range
•
Air gap
•
Worn electrode
Is spark plug okay?
Yes Go to next step.
No Replace spark plug.
4 Inspect compression pressure at suspected
faulty cylinder.
Is compression pressure correct?
(See
B–9 COMPRESSION INSPECTION .)
Yes Go to next step.
No Repair or replace malfunctioning parts.
5 Install all spark plugs.
Carry out spark test at suspected faulty cylinder.
Is strong blue spark visible?
(Compare with normal cylinder.) Yes Go to next step.
No Repair or replace malfunctioning parts.