Subaru Impreza 2003 Service Manual page 306

MECHANICAL
TROUBLE
3. Low output, hesitation and
poor acceleration
4. Surging
ENGINE TROUBLE IN GENERAL
PROBLEM PARTS, ETC.
• Engine control system <Ref. to EN(H4SO)-2, Basic Diagnostic Procedure.> or <Ref. to
EN(H4SOw/oOBD)-2, Basic Diagnostic Procedure.>
• Intake system
• Fuel line
• Belt
• Compression
• Lubrication system
• Cooling system
• Others
• Engine control system <Ref. to EN(H4SO)-2, Basic Diagnostic Procedure.> or <Ref. to
EN(H4SOw/oOBD)-2, Basic Diagnostic Procedure.>
• Intake system
• Fuel line
• Belt
• Compression
• Cooling system
• Others
ME(H4SO)-94
POSSIBLE CAUSE
• Loosened or cracked intake duct
• Loosened or cracked PCV hose
• Loosened or cracked vacuum hose
• Defective intake manifold gasket
• Defective throttle body gasket
• Defective PCV valve
• Loosened oil filler cap
• Dirty air cleaner element
• Defective fuel pump and relay
• Clogged fuel line
• Lack of or insufficient fuel
• Defective timing
• Incorrect valve clearance
• Loosened spark plugs or defective gasket
• Loosened cylinder head bolts or defective gasket
• Improper valve seating
• Defective valve stem
• Worn or broken valve spring
• Worn or stuck piston rings, cylinder and piston
• Incorrect valve timing
• Improper engine oil (low viscosity)
• Incorrect oil pressure
• Overheating
• Over cooling
• Malfunction of evaporative emission control system
• Loosened or cracked intake duct
• Loosened or cracked PCV hose
• Loosened or cracked vacuum hose
• Defective intake manifold gasket
• Defective throttle body gasket
• Defective PCV valve
• Loosened oil filler cap
• Dirty air cleaner element
• Defective fuel pump and relay
• Clogged fuel line
• Lack of or insufficient fuel
• Defective timing
• Incorrect valve clearance
• Loosened spark plugs or defective gasket
• Loosened cylinder head bolts or defective gasket
• Improper valve seating
• Defective valve stem
• Worn or broken valve spring
• Worn or stuck piston rings, cylinder and piston
• Incorrect valve timing
• Improper engine oil (low viscosity)
• Overheating
• Malfunction of evaporative emission control system
RANK
A
A
A
B
B
B
B
B
A
B
B
C
B
B
B
B
B
C
B
C
A
B
B
C
C
A
A
A
A
A
B
B
B
B
B
B
B
C
B
B
C
C
C
C
C
C
A
B
B
C