Engine Noise - Subaru 2009 IMPREZA Service Manual

28.Engine Noise

A: INSPECTION
Type of sound
Regular clicking sound
Heavy and dull clank
High-pitched clank
(Spark knock)
Clank when engine speed is
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 noise
(NOTE*)
When disconnecting the fuel injector connector, the malfunction indicator light illuminates and DTC is stored in ECM memory.
Therefore, perform the Clear Memory Mode <Ref. to EN(H4SO)(diag)-55, OPERATION, Clear Memory Mode.> and Inspection
Mode <Ref. to EN(H4SO)(diag)-44, PROCEDURE, Inspection Mode.> after connecting the 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
condition.
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)-105
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 (large end)
• Damaged engine mounting
• Loosened flywheel mounting bolt
• Ignition timing advanced
• Accumulation of carbon inside combustion chamber
• Wrong heat range of spark plug
• Improper octane value gasoline
• Worn crankshaft main bearing
• Worn connecting rod bearing (large end)
• Worn cylinder liner and piston ring
• Broken or stuck piston ring
• Worn piston pin and hole at piston end of connecting rod
• Worn cam sprocket
• Worn camshaft journal bore in cylinder head
Insufficient generator lubrication
Poor contact of generator brush and rotor
• Defective ignition starter switch
• Worn gear and starter pinion
• Loose V-belt
• Defective water pump shaft
• Insufficient compression
• Air leakage in air intake system, hose, connection or manifold
• Loose timing belt
• Timing belt contacting with adjacent part
Incorrect valve clearance
MECHANICAL