ENGINE
WG972-E4, WSM
1-S3
Rough High-speed
Operating
1. Damaged spark plug Check and adjust or replace 1-S20,
1-S21
2. Damaged ignition coil Check and replace 1-S21
3. Wires disconnection or
damaged
Check the wire harness –
Reconnect or replace –
4. Bad connection of ignition
coil and spark plug
Reconnect –
5. Improper valve clearance Check the compression pressure 1-S14
Adjust 1-S15
6. Improper intake and
exhaust valve sealing
Check the compression pressure 1-S14
Check and replace 1-S42
7. Excessive wear of rings
and liners
Check the compression pressure 1-S14
Check and replace 1-S50,
1-S56
Engine Speed Does
Not Increase
1. Damaged spark plug Check and adjust or replace 1-S20,
1-S21
2. Damaged ignition coil Check and replace 1-S21
3. Wires disconnection or
damaged
Check the wire harness –
Reconnect or replace –
4. Bad connection of ignition
coil and spark plug
Reconnect –
5. Improper input signal to
ECU
Check the wire harness
6. Clogged air cleaner Clean or replace G-14, G-24
7. Breather tube has
separated
Attach correctly 1-M5
8. Damaged throttle body Replace
Engine Suddenly
Stop
1. Insufficient fuel Check the fuel tank and refill the fuel G-10
Check the fuel system for air or leaks G-15
2. Wire disconnection or
damaged
Check the wire harness –
Reconnect or replace –
3. Clogged air cleaner Clean or replace G-14, G-24
4. Overheating of moving
parts
Check amount of engine oil G-11
Check lubricating system –
Replace oil filter cartridge G-18
5. Improper valve clearance Adjust –
Excessive Black
Exhaust Gas Is
Observed
1. Fuel system is bad Check the fuel system –
2. Fuel is extremely poor
quality
Replace fuel G-10
Excessive White
Exhaust Gas Is
Observed
1. Excessive engine oil Reduce oil to specified level 1-S25
2. Damaged valve stem seal Replace 1-S29
3. Piston ring and liner worn
or stuck
Check and replace 1-S50,
1-S56
Symptom
Probable Cause and
Checking Procedure
Solution
Reference
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