Subaru Impreza 2003 Service Manual page 308

MECHANICAL
TROUBLE
10. Excessive fuel consump-
tion
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
• Belt
• Compression
• Lubrication system
• Cooling system
• Others
ME(H4SO)-96
POSSIBLE CAUSE
• Dirty air cleaner element
• 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
• Incorrect oil pressure
• Over cooling
• Accelerator cable out of adjustment
RANK
A
A
B
B
C
C
B
C
C
B
B
C
C
B