Complaint | Symptom and possible causes | Remedy |
Engine will not start or is hard to start. | Compression too low | |
1. Tappet clearance out of adjustment | Adjust. | |
2. Worn valve guides or poor seating of valves | Repair or replace. | |
3. Mistiming valves | Adjust. | |
4. Excessively worn piston rings | Replace. | |
5. Worn-down cylinder bores | Replace. | |
6. Too slowly starter motor cranks | See electrical section. | |
7. Poor seating of spark plugs | Retighten. | |
Plug not sparking | ||
1. Fouled spark plugs | Clean. | |
2. Wet spark plugs | Clean and dry. | |
3. Defective ignition coils | Replace. | |
4. Defective ignition coil/plug caps | Replace. | |
5. Defective CKP sensor | Replace. | |
6. Defective ECM | Replace. | |
7. Open-circuited wiring connections | Repair or replace. | |
8. Open or short in high-tension cords | Replace. | |
No fuel reaching the intake manifold | ||
1. Clogged fuel filter or fuel hose | Clean or replace. | |
2. Defective fuel pump | Replace. | |
3. Defective fuel pressure regulator | Replace. | |
4. Defective fuel injector | Replace. | |
5. Defective fuel pump relay | Replace. | |
6. Defective ECM | Replace. | |
7. Open-circuited wiring connections | Check and repair. | |
Incorrect fuel/air mixture | ||
1. TP sensor out of adjustment | Adjust. | |
2. Defective fuel pump | Replace. | |
3. Defective fuel pressure regulator | Replace. | |
4. Defective TP sensor | Replace. | |
5. Defective CKP sensor | Replace. | |
6. Defective IAP sensor | Replace. | |
7. Defective ECM | Replace. | |
8. Defective ECT sensor | Replace. | |
9. Defective IAT sensor | Replace. | |
Engine idles poorly. | 1. Tappet clearance out of adjustment | Adjust. |
2. Poor seating of valves | Replace or repair. | |
3. Defective valve guides | Replace. | |
4. Worn down camshafts | Replace. | |
5. Too wide spark plug gaps | Adjust or replace. | |
6. Defective ignition coils | Replace. | |
7. Defective ignition coil/plug caps | Replace. | |
8. Defective CKP sensor | Replace. | |
9. Defective ECM | Replace. | |
10. Defective TP sensor | Replace. | |
11. Defective ISC valve | Replace. | |
12. Defective fuel pump | Replace. | |
13. Imbalanced throttle valve | Adjust. | |
14. Damaged or cracked vacuum hose | Replace. | |
Engine stalls often. | Incorrect fuel/air mixture | |
1. Defective IAP sensor or circuit | Repair or replace. | |
2. Clogged fuel filter | Clean or replace. | |
3. Defective fuel pump | Replace. | |
4. Defective fuel pressure regulator | Replace. | |
5. Defective ECT sensor | Replace. | |
6. Defective thermostat | Replace. | |
7. Defective IAT sensor | Replace. | |
8. Damaged or cracked vacuum hose | Replace. | |
Fuel injector improperly operating | ||
1. Defective fuel injectors | Replace. | |
2. No injection signal from ECM | Repair or replace. | |
3. Open or short circuited wiring connection | Repair or replace. | |
4. Defective battery or low battery voltage | Replace or recharge. | |
Control circuit or sensor improperly operating | ||
1. Defective ECM | Replace. | |
2. Defective fuel pressure regulator | Replace. | |
3. Defective TP sensor | Replace. | |
4. Defective IAT sensor | Replace. | |
5. Defective ISC valve | Replace. | |
6. Defective CKP sensor | Replace. | |
7. Defective ECT sensor | Replace. | |
8. Defective fuel pump relay | Replace. | |
Engine internal parts improperly operating | ||
1. Fouled spark plugs | Clean. | |
2. Defective CKP sensor or ECM | Replace. | |
3. Clogged fuel hose | Clean. | |
4. Out of adjustment tappet clearance | Adjust. | |
Noisy engine | Excessive valve chatter | |
1. Too large tappet clearance | Adjust. | |
2. Weakened or broken valve springs | Replace. | |
3. Worn tappet or cam surface | Replace. | |
4. Worn and burnt camshaft journal | Replace. | |
Noise seems to come from piston | ||
1. Worn down pistons or cylinders | Replace. | |
2. Carbon combustion chambers fouled with carbon | Clean. | |
3. Worn piston pins or piston pin bore | Replace. | |
4. Worn piston rings or ring grooves | Replace. | |
Noise seems to come from timing chain | ||
1. Stretched chain | Replace. | |
2. Worn sprockets | Replace. | |
3. Tension adjuster not working | Repair or replace. | |
Noise seems to come from clutch | ||
1. Worn splines of countershaft or hub | Replace. | |
2. Worn teeth of clutch plates | Replace. | |
3. Distorted clutch plates, driven and drive | Replace. | |
4. Worn clutch release bearing | Replace. | |
5. Weakened clutch dampers | Replace the primary driven gear. | |
Noise seems to come from crankshaft | ||
1. Rattling bearings due to wear | Replace. | |
2. Worn and burnt big-end bearings | Replace. | |
3. Worn and burnt journal bearings | Replace. | |
4. Too large thrust clearance | Replace thrust bearing. | |
Noise seems to come from balancer | ||
1. Worn or rubbing balancer gears | Replace. | |
Noise seems to come from transmission | ||
1. Worn or rubbing gears | Replace. | |
2. Worn splines | Replace. | |
3. Worn or rubbing primary gears | Replace. | |
4. Worn bearings | Replace. | |
Noise seems to come from water pump | ||
1. Too much play on pump shaft bearing | Replace. | |
2. Worn or damaged impeller shaft | Replace. | |
3. Worn or damaged mechanical seal | Replace. | |
4. Contact between pump case and impeller | Replace. | |
Engine runs poorly in high speed range. | Defective engine internal/electrical parts | |
1. Weakened valve springs | Replace. | |
2. Worn camshafts | Replace. | |
3. Valve timing out of adjustment | Adjust. | |
4. Too narrow spark plug gaps | Adjust. | |
5. Ignition not advanced sufficiently due to poorly working timing advance circuit | Replace ECM. | |
6. Defective ignition coils | Replace. | |
7. Defective ignition coil/plug caps | Replace. | |
8. Defective CKP sensor | Replace. | |
9. Defective ECM | Replace. | |
10. Clogged air cleaner element | Clean. | |
11. Clogged fuel hose, resulting in inadequate fuel supply to injector | Clean and prime. | |
12. Defective fuel pump | Replace. | |
13. Defective TP sensor | Replace. | |
14. Defective STP sensor or STVA | Replace. | |
Defective air flow system | ||
1. Clogged air cleaner element | Replace. | |
2. Defective throttle valve | Adjust or replace. | |
3. Defective secondary throttle valve | Adjust or replace. | |
4. Sucking air from throttle body joint | Repair or replace. | |
5. Defective ECM | Replace. | |
6. Imbalancing throttle valve synchronization | Adjust. | |
Defective control circuit or sensor | ||
1. Low fuel pressure | Repair or replace. | |
2. Defective TP sensor | Replace. | |
3. Defective IAT sensor | Replace. | |
4. Defective CMP sensor | Replace. | |
5. Defective CKP sensor | Replace. | |
6. Defective GP sensor | Replace. | |
7. Defective IAP sensor | Replace. | |
8. Defective ECM | Replace. | |
9. TP sensor out of adjustment | Replace. | |
10. Defective STP sensor and/or STVA | Replace. | |
11. Defective ISC valve | Replace. | |
Engine lacks power. | Defective engine internal/electrical parts | |
1. Loss of tappet clearance | Adjust. | |
2. Weakened valve springs | Replace. | |
3. Valve timing out of adjustment | Adjust. | |
4. Worn piston rings or cylinders | Replace. | |
5. Poor seating of valves | Repair. | |
6. Fouled spark plugs | Clean or replace. | |
7. Incorrect spark plugs | Adjust or replace. | |
8. Clogged fuel injectors | Replace. | |
9. TP sensor out of adjustment | Adjust. | |
10. Clogged air cleaner element | Replace. | |
11. Imbalancing throttle valve synchronization | Adjust. | |
12. Sucking air from throttle valve or vacuum hose | Retighten or replace. | |
13. Too much engine oil | Drain out excess oil. | |
14. Defective fuel pump or ECM | Replace. | |
15. Defective CKP sensor and ignition coils | Replace. | |
Defective control circuit or sensor | ||
1. Low fuel pressure | Repair or replace. | |
2. Defective TP sensor | Replace. | |
3. Defective IAT sensor | Replace. | |
4. Defective CKP sensor | Replace. | |
5. Defective GP sensor | Replace. | |
6. Defective IAP sensor | Replace. | |
7. Defective ECM | Replace. | |
8. Defective ISC valve | Replace. | |
9. TP sensor out of adjustment | Adjust. | |
10. Imbalanced throttle valve synchronization | Adjust. | |
11. Defective STP sensor and/or STVA | Replace. | |
12. Defective EXCVA | Replace. | |
Engine overheats | Defective engine internal parts | |
1. Heavy carbon deposit on piston crowns | Clean. | |
2. Not enough oil in the engine | Add oil. | |
3. Defective oil pump or clogged oil circuit | Replace or clean. | |
4. Sucking air from intake pipes | Retighten or replace. | |
5. Use incorrect engine oil | Change. | |
6. Defective cooling system | See radiator section. | |
Lean fuel/air mixture | ||
1. Short-circuited IAP sensor/lead wire | Repair or replace. | |
2. Short-circuited IAT sensor/lead wire | Repair or replace. | |
3. Sucking air from intake pipe joint | Repair or replace. | |
4. Defective fuel injectors | Replace. | |
5. Defective ECT sensor | Replace. | |
Other factors | ||
1. Ignition timing is too advanced due to defective timing advance system (ECT sensor, GP sensor, CKP sensor and ECM). | Replace. | |
Dirty or heavy exhaust smoke | 1. Too much engine oil in the engine | Check with inspection window, drain out excess oil. |
2. Worn piston rings or cylinders | Replace. | |
3. Worn valve guides | Replace. | |
4. Scored or scuffed cylinder walls | Replace. | |
5. Worn valves stems | Replace. | |
6. Defective stem seal | Replace. | |
7. Worn oil ring side rails | Replace. | |
Slipping clutch | 1. Weakened clutch springs | Replace. |
2. Worn or distorted pressure plates | Replace. | |
3. Distorted clutch plates or pressure plates | Replace. | |
4. Clutch release screw out of adjustment | Adjust | |
Dragging clutch | 1. Some clutch spring weakened while others are not. | Replace. |
2. Distorted pressure plates or clutch plates | Replace. | |
3. Clutch release screw out of adjustment | Adjust | |
Transmission will not shift. | 1. Broken gearshift cam | Replace. |
2. Distorted gearshift forks | Replace. | |
3. Worn gearshift pawl | Replace. | |
Transmission will not shift back. | 1. Broken return spring on shift shaft | Replace. |
2. Rubbing or stickily shift shaft | Repair or replace. | |
3. Distorted or worn gearshift forks | Replace. | |
Transmission jumps out of gear. | 1. Worn shifting gears on driveshaft or countershaft | Replace. |
2. Distorted or worn gearshift forks | Replace. | |
3. Weakened stopper spring on gearshift stopper | Replace. | |
4. Worn gearshift cam plate | Replace. |