Subaru Impreza 3 / Impreza WRX / Impreza WRX STI. Manual — part 182

ME(w/o STI)-109

Engine Noise

MECHANICAL

26.Engine Noise

A: INSPECTION

*

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(H4DOTC)(diag)-63, OPERATION, Clear Memory Mode.> and Inspec-
tion Mode <Ref. to EN(H4DOTC)(diag)-49, PROCEDURE, Inspection Mode.> after connecting the fuel injector connector.

Type of sound

Condition

Possible cause

Regular clicking sound

Sound increases as engine
speed increases.

• Valve mechanism is defective.
• Incorrect valve clearance
• Worn camshaft
• Broken valve spring

Heavy and dull clank

Oil pressure is low.

• Worn crankshaft main bearing
• Worn connecting rod bearing (large end)

Oil pressure is normal.

• Loosened flywheel mounting bolt
• Damaged engine mounting

High-pitched clank

Sound is noticeable when
accelerating with an overload
condition.

• Ignition timing advanced
• Accumulation of carbon inside combustion chamber
• Wrong heat range of spark plug
• Improper octane value gasoline

Clank when engine speed is
between 1,000 and 2,000
rpms.

Sound is reduced when the fuel
injector connector of the noisy
cylinder is disconnected.

*

• Worn crankshaft main bearing
• Worn connecting rod bearing (large end)

Knocking sound when engine
is operating under idling
speed and engine is warm

Sound is reduced when the fuel
injector connector of the noisy
cylinder is disconnected.

*

• Worn cylinder liner and piston ring
• Broken or stuck piston ring
• Worn piston pin and hole at piston end of connecting rod

Sound is not reduced if each
fuel injector connector is dis-
connected in turn.

*

• Unusually worn valve lifter
• Worn cam sprocket
• Worn camshaft journal bore in cylinder head

Squeaky sound

—

• Insufficient generator lubrication

Rubbing sound

—

• Poor contact of generator brush and rotor

Gear scream when starting
engine

—

• Defective ignition starter switch
• Worn gear and starter pinion

Sound like polishing glass
with a dry cloth

—

• Loose V-belt
• Defective water pump shaft

Hissing sound

—

• Insufficient compression
• Air leakage in air intake system, hose, connection or manifold

Timing belt noise

—

• Loose timing belt
• Timing belt contacting with adjacent part

Valve noise

—

• Incorrect valve clearance

ME(w/o STI)-110

Engine Noise

MECHANICAL

EXHAUST

EX(w/o STI)

Page

1.

General Description . . . . . . . . . . . . . . . . . . . . ...2

EX(w/o STI)-2

General Description

EXHAUST

1. General Description

A: SPECIFICATION

Specifications for models other than STI model are

included in the EX (STI) section. <Ref. to EX(STI)-

2, General Description.>