Mazda Mazda6 Workshop Manual Supplement page 369

NO.21 ENGINE NOISE
21 ENGINE NOISE
• Engine noise under hood.
DESCRIPTION
• Engine internal damage
• Timing belt displacement
• Fuel injector malfunction
• Loose attaching bolts or worn parts
• Improper drive belt tension
• Air leakage from intake-air system
• Incorrect injection timing
• Erratic signal from CKP sensor
• Erratic signal from CMP sensor
• Fuel pressure sensor or related circuit malfunction
• Boost sensor or related circuit malfunction
• Accelerator position sensor or related circuit malfunction
• MAF/IAT sensor or related circuit malfunction
• ECT sensor or related circuit malfunction
• EGR system or malfunction
• IAT sensor No.2 or related circuit malfunction
• Vacuum leakage
• Suction control valve malfunction (built-in supply pump)
POSSIBLE
• Air leakage from intake-air system
CAUSE
• Air in power steering fluid line
• Turbocharger operating noise
• Solenoid valve operating noise
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 injury 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.
Note
• PCM checks fuel injection amount during a set interval while idling, and automatically corrects it to
maintain engine efficiency. It is normal that engine noise and vibration might be a little louder during
this process.
Diagnostic Procedure
STEP INSPECTION
1 Is squeal, click or chirp sound present?
2 Is rumble or grind sound present?
3 Is rattle sound present?
4 Is hiss sound present?
5 Is rap or roar sound present?
TROUBLESHOOTING
RESULTS
Yes Inspect engine oil level, solenoid valves installation or
drive belt.
No Go to next step.
Yes Inspect drive belt tension or power steering system
fluid level.
If okay, perform power steering fluid line air bleed.
No Go to next step.
Yes Inspect location of rattle for loose parts.
No Go to next step.
Yes Inspect for vacuum leakage and intake-air system
leakage.
No Go to next step.
Yes Inspect exhaust system or loose parts.
No Go to next step.
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ACTION
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F2