Subaru EX13 Service Manual page 103

Problem and possible cause
1 . Insufficient compression
2 . Ignition system problems
3 . Fuel system malfunction
4 . Low air intake volume
1 . Engine
1 . Trottle body
2 . Intake system
3 . Cylinder head
4 . Valve system
5 . Ignition system
1) Loosen spark plug
2) Leakage from cylinder head gasket
3) Piston ring seizure or wear
4) Piston or cylinder wear
5) Incorrect valve and seat contact
6) Valve stem seizure
7) Improper valve clearance
1) Faulty spark plug
2) Faulty ignition coil
3) Improper air gap between ignition coil and flywheel
4) Demagnetization (flywheel magneto)
5) Bad EFI wire harness
1) Throttle body clogged
2) Fuel strainer and/or hose clogged
3) Air in fuel lines
4) Leaky fuel pump pulse line
5) Poor quality gasoline or water in gasoline
6) Bad EFI wire harness
1) Air cleaner clogged
2) Throttle valve malfunction
1) Cooling air flow obstructed at inlet or cylinder baffle
portion
2) Poor quality engine oil
3) Lean fuel/air mixture
4) Excessive back pressure of exhaust system
5) Overloading
1) Low idling speed
1) Air mixing from air intake system joints
1) Gasket faulty (blow-by)
1) Improper valve clearance
2) Leakage from valve seat
3) Excessive clearance between valve stem and guide
1) Weak spark
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Remedy
Retighten; replace gasket
Retighten; replace gasket
Replace
Repair or replace
Repair or replace
Repair or replace
Adjust
Replace
Replace
Adjust
Replace
Replace
Inspect, replace
Clean or replace
Check and retighten joints
Replace
Replace
Replace
Clean or replace
Repair or replace
Clean
Replace
Check and adjust carburetor
Check and clean or replace
Adjust to rated load
Adjust
Check and tighten;
replace gasket
Replace
Adjust
Repair
Replace
Check; adjust or replace
plug