Engine Noise - Subaru IMPREZA 2002 Service Manual

ENGINE NOISE
MECHANICAL
23.Engine Noise
A: INSPECTION
Type of sound
Condition Possible cause
Valve mechanism is defective.
Incorrect valve clearance
Worn valve rocker
Worn camshaft
Broken valve sDrina
Sound increases as engine
speed increases.
Regular clicking sound
Worn crankshaft main bearing
Worn connecting rod bearing (big end)
Oil pressure is low.
Heavy and dull clank
Oil pressure is normal.
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
High-pitched clank (Spark
knock)
Sound is noticeable when
accelerating with an overload.
Sound is reduced when fuel
injector connector of noisy cyl-
inder is disconnected.
(NOTE*)
Clank when engine speed is
medium (1,000 to 2,000 rpm).
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
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*)
Knocking sound when engine
is operating under idling speed
and engine is warm
G e a k r s o u n d
Insufficient generator lubrication
RubbinQ sound
Defective generator brush and rotor contact
Defective ignition starter switch
Worn aear and starter Dinion
Gear scream when starting
engine
Sound like polishing glass with
a drv cloth
Loose drive belt
Defective water pump shaft
Loss of compression
Air leakage in air intake system, hoses, connections or mani-
folds
Hissing sound
Loose timing belt
Belt contacting case/adjacent part
Incorrect valve clearance
Timing belt noise
Valve tappet noise
NOTE*:
When disconnecting the fuel injector connector, Malfunction Indicator Light (CHECK ENGINE light) illuminates and trouble code
is stored in ECM memory.
Therefore, carry out the CLEAR MEMORY MODE <Ref. to EN(S0HC)-43, OPERATION, Clear Memory Mode.> and INSPEC-
TION MODE <Ref. to EN(S0HC)-40, OPERATION, Inspection Mode.> after connecting the fuel injector connector.
ME(SOHC)-SS