Notes:
- This is not an exhaustive list, giving every possible cause for each problem listed. It is meant simply as a rough guide to assist the troubleshooting for some of the more common difficulties.
- The ECU may be involved in the DFI electrical and ignition system troubles. If these parts and circuits checked out good, be sure to check the ECU for ground and power supply. If the ground and power supply are checked good, replace the ECU.
Engine doesn't start, starting difficulty
Symptoms or Possible Causes | Actions (chapter) |
Starter motor not rotating | |
Ignition and engine stop switches not ON | Turn both switches ON. |
Starter lockout switch or neutral switch trouble | Inspect (see chapter 16). |
Starter motor trouble | Inspect (see chapter 16). |
Battery voltage low | Inspect and charge (see chapter 16). |
Starter relays not contacting or operating | Inspect the starter relay (see chapter 16). |
Starter button not contacting | Inspect and replace (see chapter 16). |
Starter system wiring open or shorted | Inspect the wiring (see chapter 16). |
Ignition switch trouble | Inspect and replace (see chapter 16). |
Engine stop switch trouble | Inspect and repair or replace (see chapter 16). |
Main 30 A or ignition fuse blown | Inspect and replace (see chapter 16). |
Starter motor rotating but engine doesn't turn over | |
Starter clutch trouble | Inspect (see chapter 9). |
Starter idle gear trouble | Inspect (see chapter 9). |
Engine won't turn over | |
Valve seizure | Inspect and replace (see chapter 5). |
Rocker arm seizure | Inspect and replace (see chapter 5). |
Cylinder, piston seizure | Inspect and replace (see chapter 5). |
Camshaft seizure | Inspect and replace (see chapter 5). |
Connecting rod small end seizure | Inspect and replace (see chapter 9). |
Connecting rod big end seizure | Inspect and replace (see chapter 9). |
Crankshaft seizure | Inspect and replace (see chapter 9). |
Transmission gear or bearing seizure | Inspect and replace (see chapter 9). |
Balancer bearing seizure | Inspect and replace (see chapter 9). |
No fuel flow | |
No or little fuel in tank | Supply fuel (see Owner's Manual). |
Fuel pump not rotating | Inspect (see chapter 3). |
Fuel injector trouble | Inspect and replace (see chapter 3). |
Fuel tank air vent obstructed | Inspect and repair (see chapter 3). |
Fuel filter or pump screen clogged | Inspect and replace fuel pump (see chapter 3) |
Fuel pressure regulator clogged | Inspect and replace fuel pump (see chapter 3). |
Fuel line clogged | Inspect and repair (see chapter 3). |
Engine flooded | |
Spark plug dirty, broken or gap maladjusted | Clean spark plugs and adjust plug gap (see chapter 2). |
Starting technique faulty | When flooded, don't crank engine with throttle fully opened. |
No spark or spark weak | |
Ignition and engine stop switches not ON | Turn both switches ON. |
Clutch lever not pulled in and gear not in neutral whether sidestand up or not | Pull the lever in and shift the gear in neutral. |
Though clutch lever pulled in but sidestand up and gear not in neutral | Sidestand down and clutch lever pulled inwhether gear in neutral, or not. |
Vehicle-down sensor coming off | Reinstall (see chapter 3). |
Vehicle-down sensor trouble | Inspect (see chapter 3). |
ECU ground or power supply trouble | Inspect (see chapter 3). |
Battery voltage low | Inspect and charge (see chapter 16). |
Spark plug dirty, broken or gap maladjusted | Clean spark plug and adjust plug gap (see chapter 2). |
Spark plug cap or high tension wiring trouble | Inspect the ignition coil (see chapter 16). |
Spark plug cap shorted or not in good contact | Reinstall or inspect the cap (see chapter 16). |
Spark plug incorrect | Replace it with the correct plug (see chapter 16). |
IC igniter in ECU trouble | Inspect (see chapter 16). |
Neutral, starter lockout or sidestand switch trouble | Inspect each switch (see chapter 16). |
Crankshaft sensor trouble | Inspect (see chapter 16). |
Ignition coil trouble | Inspect (see chapter 16). |
Ignition switch shorted | Inspect and replace (see chapter 16). |
Engine stop switch shorted | Inspect and repair or replace (see chapter 16). |
Starter system wiring shorted or open | Inspect and repair or replace (see chapter 16). |
Main 30 A or ignition fuse blown | Inspect and replace (see chapter 16). |
Fuel/air mixture incorrect | |
Air cleaner clogged, poorly sealed or missing | Clean or reinstall (see chapter 3). |
Leak from oil filler cap, crankcase breather hose or air cleaner drain hose | Inspect and repair or replace (see chapter 3). |
Water or foreign matter in fuel | Change fuel. Inspect and clean fuel system (see chapter 3). |
Fuel pressure regulator trouble | Inspect fuel pressure and replace fuel pump (see chapter 3). |
Throttle sensor trouble | Inspect (see chapter 3). |
Fuel pressure may be low | Inspect (see chapter 3). |
Fuel pump trouble | Inspect (see chapter 3). |
Fuel injector trouble | Inspect (see chapter 3). |
Inlet air pressure sensor trouble | Inspect (see chapter 3). |
Inlet air temperature sensor trouble | Inspect (see chapter 3). |
Water temperature sensor trouble | Inspect (see chapter 3). |
Throttle valves or actuator trouble | Inspect (see chapter 3). |
Crankshaft sensor trouble | Inspect (see chapter 3). |
Compression low | |
Spark plug loose | Reinstall (see chapter 16). |
Cylinder head not sufficiently tightened down | Tighten (see chapter 5). |
Cylinder, piston worn | Inspect and replace (see chapter 5). |
Piston ring bad (worn, weak, broken or sticking) | Inspect and replace (see chapter 5). |
Piston ring/groove clearance excessive | Inspect and replace (see chapter 5). |
Cylinder head gasket damaged | Replace (see chapter 5). |
Cylinder head warped | Inspect and replace (see chapter 5). |
Valve guide worn | Inspect and replace (see chapter 5). |
Valve spring broken or weak | Inspect and replace (see chapter 5). |
Valve not seating properly (valve bent, worn or carbon accumulating on seating surface) | Inspect and repair or replace (see chapter 5). |
Poor running at low speed
Symptoms or Possible Causes | Actions (chapter) |
Spark weak | |
Battery voltage low | Inspect and charge (see chapter 16). |
Spark plug dirty, broken, or gap maladjusted | Clean spark plugs and adjust plug gap (see chapter 2). |
Spark plug cap or high tension wiring trouble | Inspect the ignition coil (see chapter 16). |
Spark plug cap shorted or not in good contact | Reinstall or inspect the cap (see chapter 16). |
Spark plug incorrect | Replace it with the correct plug (see chapter 16). |
IC igniter in ECU trouble | Inspect (see chapter 16). |
Crankshaft sensor trouble | Inspect (see chapter 16). |
Ignition coil trouble | Inspect (see chapter 16). |
Fuel/air mixture incorrect | |
Little fuel in tank | Supply fuel (see Owner's Manual). |
Air cleaner clogged, poorly sealed, or missing | Clean element or inspect sealing (see chapter 3). |
Air cleaner duct loose | Reinstall (see chapter 3). |
Air cleaner O-ring damaged | Replace (see chapter 3). |
Fuel tank air vent obstructed | Inspect and repair (see chapter 3). |
Throttle body assy loose | Reinstall (see chapter 3). |
Throttle body assy O-ring damage | Replace (see chapter 3). |
Throttle valves or actuator trouble | Push in (see chapter 3). |
Fuel filter or pump screen clogged | Inspect and replace fuel pump (see chapter 3). |
Fuel pressure regulator clogged | Inspect fuel pressure and replace fuel pump (see chapter 3). |
Fuel line clogged | Inspect and repair (see chapter 3). |
Thermostat trouble | Inspect and replace (see chapter 4). |
Inlet air temperature sensor trouble | Inspect (see chapter 3). |
Inlet air pressure sensor trouble | Inspect (see chapter 3). |
Unstable (rough) idling | |
Throttle valves or actuator trouble | Inspect (see chapter 3). |
Fuel injector trouble | Inspect (see chapter 3). |
Throttle sensor trouble | Inspect (see chapter 3). |
Inlet air temperature sensor trouble | Inspect (see chapter 3). |
Water temperature sensor trouble | Inspect (see chapter 3). |
Fuel pressure too low or too high | Inspect (see chapter 3). |
Battery voltage low | Inspect and charge (see chapter 16). |
Incorrect idle speed | |
Water temperature sensor trouble | Inspect (see chapter 3). |
Throttle sensor trouble | Inspect (see chapter 3). |
Throttle valves or actuator trouble | Inspect (see chapter 3). |
Engine stalls easily | |
Fuel pump trouble | Inspect (see chapter 3). |
Fuel injector trouble | Inspect (see chapter 3). |
Throttle sensor trouble (engine stops when opening the throttle) | Inspect (see chapter 3). |
Fuel pressure too low or too high | Inspect (see chapter 3). |
Inlet air temperature sensor trouble | Inspect (see chapter 3). |
Fuel pressure too low or too high | Inspect (see chapter 3). |
Fuel pressure regulator trouble | Inspect and replace (see chapter 3). |
Crankshaft sensor trouble | Inspect (see chapter 16). |
Ignition coil trouble | Inspect (see chapter 16). |
Compression Low | |
Spark plug loose | Reinstall (see chapter 16). |
Cylinder head not sufficiently tightened down | Tighten (see chapter 5). |
Cylinder, piston worn | Inspect and replace (see chapter 5). |
Piston ring bad (worn, weak, broken or sticking) | Inspect and replace (see chapter 5). |
Piston ring/groove clearance excessive | Inspect and replace (see chapter 5). |
Cylinder head gasket damaged | Replace (see chapter 5). |
Cylinder head warped | Inspect and replace (see chapter 5). |
Valve guide worn or stem seal damaged | Inspect and replace (see chapter 5). |
Valve spring broken or weak | Inspect and replace (see chapter 5). |
Valve not seating properly (valve bent, worn or carbon accumulating on seating surface) | Inspect and repair or replace (see chapter 5). |
Camshaft cam worn | Inspect and replace (see chapter 5). |
Hesitation | |
Too low fuel pressure | Inspect (see chapter 3). |
Clogged fuel line | Inspect and repair (see chapter 3). |
Cracked or obstructed inlet air pressure sensor hose | Inspect and repair or replace (see chapter 3). |
Fuel pump trouble | Inspect (see chapter 3). |
Fuel injector trouble | Inspect (see chapter 3). |
Inlet air temperature sensor trouble | Inspect (see chapter 3). |
Throttle sensor malfunction | Inspect (see chapter 3). |
Water temperature sensor trouble | Inspect (see chapter 3). |
Inlet air pressure sensor trouble | Inspect (see chapter 3). |
Loose injector connectors | Remedy (see chapter 3). |
Crankshaft sensor trouble | Inspect and repair or replace (see chapter 16). |
Ignition coil trouble | Inspect and repair or replace (see chapter 16). |
Loose terminal of battery (-) lead or engine ground lead | Inspect and repair (see chapter 16). |
Delay of ignition timing | Inspect crankshaft sensor and IC igniter in ECU (see chapter 16). |
Poor acceleration | |
Too low fuel pressure | Inspect (see chapter 3). |
Water or foreign matter in fuel | Change fuel. Inspect and clean fuel system (see chapter 3) |
Clogged fuel filter | Inspect (see chapter 3) and replace fuel pump. |
Fuel pump trouble | Inspect (see chapter 3). |
Fuel injector trouble | Inspect (see chapter 3) |
Inlet air temperature sensor trouble | Inspect (see chapter 3). |
Water temperature sensor trouble | Inspect (see chapter 3). |
Ignition coil trouble | Inspect and replace (see chapter 16). |
Engine oil level too high | Repair (see chapter 7) |
Spark plug dirty, broken or gap maladjusted | Clean spark plugs and adjust plug gap (see chapter 2) |
Stumble | |
Too low fuel pressure | Inspect (see chapter 3). |
Fuel injector trouble | Inspect (see chapter 3). |
Throttle sensor malfunction | Inspect (see chapter 3). |
Water temperature sensor trouble | Inspect (see chapter 3). |
Inlet air pressure sensor trouble | Inspect (see chapter 3). |
Surge | |
Unstable fuel pressure | Fuel pressure regulator trouble (Inspect and replace fuel pump) or kinked fuel line (Inspect and repair fuel line) (see chapter 3). |
Fuel injector trouble | Inspect (see chapter 3). |
Water temperature sensor trouble | Inspect (see chapter 3). |
Backfiring when deceleration | |
Spark plug dirty, broken or gap maladjusted | Clean spark plugs and adjust plug gap (see chapter 2) |
Too low fuel pressure | Inspect (see chapter 3). |
Crankshaft sensor trouble | Inspect (see chapter 3). |
Fuel pump trouble | Inspect (see chapter 3). |
Throttle sensor malfunction | Inspect (see chapter 3). |
Inlet air temperature sensor trouble | Inspect (see chapter 3). |
Water temperature sensor trouble | Inspect (see chapter 3). |
Inlet air pressure sensor trouble | Inspect (see chapter 3). |
Air switching valve broken | Inspect and replace (see chapter 5 or 16). |
Air suction valve trouble | Inspect and replace (see chapter 5). |
After fire | |
Spark plug burned or gap maladjusted | Adjust plug gap or replace plug (see chapter 16). |
Crankshaft sensor trouble | Inspect (see chapter 3). |
Inlet air temperature sensor trouble | Inspect (see chapter 3). |
Water temperature sensor trouble | Inspect (see chapter 3). |
Inlet air pressure sensor trouble | Inspect (see chapter 3). |
Fuel injector trouble | Inspect (see chapter 3). |
Run-on (dieseling) | |
Ignition switch trouble | Inspect and replace (see chapter 16). |
Engine switch trouble | Inspect and repair or replace (see chapter 16). |
Fuel injector trouble | Inspect (see chapter 3). |
Engine overheating | (see Overheating of Troubleshooting Guide, see chapter 17) |
Other | |
Engine oil viscosity too high | Change (see chapter 2). |
Drive belt trouble | Inspect and replace (see chapter 11). |
Brake dragging | Inspect caliper fluid seal damage or clogging of master cylinder relief and supply ports (see chapter 12). |
Clutch slipping | Inspect friction plates for wear (see chapter 6). |
Engine overheating | (see Overheating of Troubleshooting Guide in chapter 17 |
Air switching valve trouble | Inspect and replace (see chapter 16). |
Air suction valve trouble | Inspect and replace (see chapter 5). |
Intermittent any DFI fault and its recovery | Check that DFI connectors are clean and tight, and examine wires for signs of burning or fraying (see chapter 3). |
Poor running or no power at high speed
Symptoms or Possible Causes | Actions (detailed reference) |
Firing incorrect | |
Spark plug dirty, broken or maladjusted | Clean spark plug and adjust plug gap (see chapter 2). |
Spark plug cap or high tension wiring trouble | Inspect plug cap and ignition coil (see chapter 16). |
Spark plug cap shorted or not in good contact | Reinstall or inspect the cap (see chapter 16). |
Spark plug incorrect | Replace it with the correct plug (see chapter 16) |
IC igniter in ECU trouble | Inspect (see chapter 16). |
Crankshaft sensor trouble | Inspect (see chapter 16). |
Ignition coil trouble | Inspect (see chapter 16). |
Fuel/mixture incorrect | |
Air cleaner clogged, poorly sealed, or missing | Clean element or inspect sealing (see chapter 3). |
Air cleaner duct loose | Reinstall (see chapter 3). |
Air cleaner O-ring damaged | Replace (see chapter 3). |
Water or foreign matter in fuel | Change fuel. Inspect and clean fuel system (see chapter 3). |
Throttle body assy loose | Reinstall (see chapter 3). |
Throttle body assy O-ring damaged | Replace (see chapter 3). |
Fuel tank air vent obstructed | Inspect and repair (see chapter 3). |
Fuel line clogged | Inspect and repair (see chapter 3). |
Fuel pump operates intermittently and often DFI fuse blows. | Pump bearings may wear. Replace the pump (see chapter 3). |
Fuel pump trouble | Inspect (see chapter 3). |
Inlet air temperature sensor trouble | Inspect (see chapter 3). |
Throttle sensor malfunction | Inspect (see chapter 3). |
Inlet air pressure sensor trouble | Inspect (see chapter 3). |
Cracked or obstructed inlet air pressure sensor hose | Inspect and repair or replace (see chapter 3) |
Injector clogged | Visually inspect and replace (see chapter 3) |
Compression low | |
Spark plug loose | Reinstall (see chapter 16). |
Cylinder head not sufficiently tightened down | Tighten (see chapter 5). |
Cylinder, piston worn | Inspect and replace (see chapter 5). |
Piston ring bad (worn, weak, broken or sticking) | Inspect and replace (see chapter 5). |
Piston ring/groove clearance excessive | Inspect and replace (see chapter 5). |
Cylinder head gasket damaged | Replace (see chapter 5). |
Cylinder head warped | Inspect and replace (see chapter 5). |
Valve spring broken or weak | Inspect and replace (see chapter 5). |
Valve not seating properly (valve bent, worn or carbon accumulating on the seating surface) | Inspect and repair or replace (see chapter 5). |
Knocking | |
Carbon buit up in combustion chamber | Repair (see chapter 5). |
Fuel poor quality or incorrect (Use high-octone gasoline recommended in the Owner's Manual) | Change fuel (see chapter 3). |
Spark plug incorrect | Replace it with the correct plug (see chapter 16) |
Ignition coil trouble | Inspect (see chapter 16). |
IC igniter in ECU trouble | Inspect (see chapter 16). |
Inlet air temperature sensor trouble | Inspect (see chapter 3). |
Miscellaneous | |
Throttle valves won't fulley open | Inspect throttle cable and lever linkage (see chapter 3). |
Brake dragging | Inspect caliper fluid seal damage or clogging of master cylinder relief and supply ports (see chapter 12). |
Clutch slipping | Inspect friction plates for wear (see chapter 6). |
Engine overheating | (see Overheating of Troubleshooting Guide in chapter 17) |
Engine oil level too high | Repair (see chapter 7). |
Engine oil viscosity too high | Change (see chapter 3). |
Drive belt trouble | Inspect and replace (see chapter 11). |
Camshaft cam worn | Inspect and replace (see chapter 5). |
Air switching valve trouble | Inspect and replace (see chapter 5 or 16). |
Air suction valve trouble | Inspect and replace (see chapter 5). |
Catalytic converters melt down due to muffler overheating | Replace muffler (see chapter 5). |
Exhaust Smokes Excessively | |
White smokes | |
Piston oil ring worn | Inspect and replace (see chapter 5). |
Cylinder worn | Inspect and replace (see chapter 5). |
Valve oil seal damaged | Replace (see chapter 5). |
Valve guide worn | Replace the guide (see chapter 5). |
Engine oil level too high | Repair (see chapter 7). |
Black smoke | |
Air cleaner clogged | Clean (see chapter 3). |
Too high fuel pressure | Inspect (see chapter 3). |
Injection stuck open | Inspect (see chapter 3). |
Water temperature sensor trouble | Inspect and replace (see chapter 3). |
Inlet air temperature sensor trouble | Inspect and replace (see chapter 3). |
Brown smoke | |
Air cleaner duct loose | Reinstall (see chapter 3). |
Air cleaner O-ring damaged | Replace (see chapter 3). |
Too low fuel pressure | Inspect (see chapter 3). |
Water temperature sensor trouble | Inspect and replace (see chapter 3). |
Inlet air temperature sensor trouble | Inspect and replace (see chapter 3). |