Subaru IMPREZA 2004 Service Manual page 190

MECHANICAL
TROUBLE
10. Excessive fuel consump-
tion
Engine Trouble in General
PROBLEM PARTS, ETC.
Engine control system <Ref. to EN(H4SO)(diag)-2, Basic Diagnostic Procedure.> or
<Ref. to EN(H4SOw/oOBD)(diag)-2, Basic Diagnostic Procedure.>
Intake system
Belt
Compression
Lubrication system
Cooling system
Others
ME(H4SO)-94
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