Subaru Impreza 2003 Service Manual page 309

23.Engine Noise
A: INSPECTION
Type of sound
Regular clicking sound
Heavy and dull clank
High-pitched clank (Spark
knock)
Clank when engine speed is
medium (1,000 to 2,000 rpm).
Knocking sound when engine
is operating under idling speed
and engine is warm
Squeaky sound
Rubbing sound
Gear scream when starting
engine
Sound like polishing glass with
a dry cloth
Hissing sound
Timing belt noise
Valve tappet noise
NOTE*:
When disconnecting the fuel injector connector, Malfunction Indicator Light illuminates and DTC is stored in ECM memory.
Therefore, carry out the CLEAR MEMORY MODE <Ref. to EN(H4SO)-46, OPERATION, Clear Memory Mode.> or <Ref. to
EN(H4SOw/oOBD)-28, OPERATION, Clear Memory Mode.> and INSPECTION MODE <Ref. to EN(H4SO)-39, OPERATION,
Inspection Mode.> or <Ref. to EN(H4SOw/oOBD)-26, OPERATION, Inspection Mode.> after connecting fuel injector connector.
ENGINE NOISE
Condition
Sound increases as engine
speed increases.
Oil pressure is low.
Oil pressure is normal.
Sound is noticeable when
accelerating with an overload.
Sound is reduced when fuel
injector connector of noisy cyl-
inder is disconnected.
(NOTE*)
Sound is reduced when fuel
injector connector of noisy cyl-
inder is disconnected.
(NOTE*)
Sound is not reduced if each
fuel injector connector is dis-
connected in turn. (NOTE*)
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ME(H4SO)-97
Possible cause
• Valve mechanism is defective.
• Incorrect valve clearance
• Worn valve rocker
• Worn camshaft
• Broken valve spring
• Worn crankshaft main bearing
• Worn connecting rod bearing (big end)
• Loose flywheel mounting bolts
• Damaged engine mounting
• Ignition timing advanced
• Accumulation of carbon inside combustion chamber
• Wrong spark plug
• Improper gasoline
• Worn crankshaft main bearing
• Worn bearing at crankshaft end of connecting rod
• Worn cylinder liner and piston ring
• Broken or stuck piston ring
• Worn piston pin and hole at piston end of connecting rod
• Unusually worn valve lifter
• Worn cam gear
• Worn camshaft journal bore in crankcase
• Insufficient generator lubrication
• Defective generator brush and rotor contact
• Defective ignition starter switch
• Worn gear and starter pinion
• Loose drive belt
• Defective water pump shaft
• Loss of compression
• Air leakage in air intake system, hoses, connections or mani-
folds
• Loose timing belt
• Belt contacting case/adjacent part
• Incorrect valve clearance
MECHANICAL