Troubleshooting Engine [Toyota Highlander XU20]

1. The engine does not turn when trying to start

• 1. Loosening or damage to the connection of the battery terminals due to corrosion (chapter 1).
• 2. The battery is discharged or faulty (chapter 1)
• 3. The P position in the automatic transmission is not engaged (chapter 7).
• 4. Break, disconnection or loosening of the starting circuit wiring (chapter 5 and 12).
• 5. Seizure of the starter gear in the flywheel ring gear (chapter 5).
• 6. Malfunction of the starter solenoid (chapter 5).
• 7. Starter malfunction (chapter 5).
• 8. Ignition switch malfunction (chapter 12).
• 9. Wear or breakage of the starter gear teeth or flywheel ring gear (chapter 5).

2. The engine turns but does not start

• 1. Empty fuel tank.
• 2. The battery is discharged (the engine is turning slowly) (chapter 5).
• 3. Loosening or damage to the connection of the battery terminals due to corrosion (chapter 1).
• 4. Leaking injector(s), faulty fuel pump, pressure regulator, etc. (chapter 4).
• 5. Fuel does not enter the fuel rail (chapter 4).
• 6. Ignition system components are wet or damaged (chapter 5).
• 7. Worn, faulty or incorrectly adjusted spark plug gap (chapter 1).
• 8. Break, disconnection or loosening of the starting circuit wiring (chapter 5).
• 9. Break, disconnection or loosening of ignition coil wiring or ignition coil malfunction (chapter 5).
• 10. Malfunction of the camshaft or crankshaft position sensor (chapter 6).

3. Starting a cold engine is difficult

• 1. The battery is discharged or weakly charged (chapter 5).
• 2. Fuel system malfunction (chapter 4).
• 3. Cold start injector malfunction (chapter 4).
• 4. Leak in the injector (chapter 4).
• 5. Coolant temperature sensor malfunction (chapter 6).

4. Starting a warm engine is difficult

• 1. The air filter is clogged (chapter 1).
• 2. Fuel does not enter the fuel injection system (chapter 4).
• 3. Damage due to corrosion of the battery terminal connections, especially the ground wire connections (chapter 1).

5. Increased noise or uneven operation of the starter when switched on

• 1. Wear or breakage of the starter gear teeth or flywheel ring gear (chapter 5).
• 2. Loose or missing starter mounting bolts (chapter 5).

6. The engine starts but immediately stalls

• 1. Loose or faulty electrical connections in the ignition coil or generator circuits (chapter 5).
• 2. Not enough fuel is supplied to the fuel injector) (chapter 1 and 4).
• 3. Vacuum loss through the gasket between the intake manifold/storage chamber and the throttle body (chapter 1 and 4).

7. Oil leaks under the engine

• 1. Leak through the oil pan gasket and/or drain plug gasket (chapter 2).
• 2. Leak at the installation site of the oil pressure sensor (chapter 2).
• 3. Leaks through the cylinder head gasket (chapter 2).
• 4. Engine seal leaks (chapter 2).
• 5. Leak in the oil pump housing (chapter 2).

8. Violation of stability in idle mode

• 1. Loss of vacuum (chapter 2 and 4).
• 2. EGR valve leak (chapter 6).
• 3. Clogged air filter (chapter 1).
• 4. The fuel pump does not provide the required fuel flow (chapter 4).
• 5. Leakage through the cylinder head gasket (chapter 2).
• 6. Wear of the timing belt or toothed pulleys (chapter 2).
• 7. Wear of camshaft cams (chapter 2).

9. Misfiring in idle mode

• 1. Worn or faulty spark plugs (chapter 1).
• 2. Malfunction of spark plug wires (chapter 1).
• 3. Loss of vacuum (chapter 4).
• 4. Malfunction in the engine management system (chapter 6).
• 5. Inequality or low compression value in the cylinders (chapter 2).

10. Misfires during engine operation throughout the entire speed range

• 1. Clogged fuel filter and/or dirt in the fuel system (chapter 1).
• 2. Low fuel injector performance (chapter 4).
• 3. Malfunction or wear of spark plugs (chapter 1).
• 4. Malfunction in the engine management system (chapter 6)
• 5. Malfunction of elements of the emission reduction systems (chapter 6).
• 6. Inequality or low compression value in the cylinders (chapter 2).
• 7. Wear or damage to the ignition coil (chapter 5).

11. The engine runs unsteadily when accelerating

• 1. Spark plug contamination (chapter 1).
• 2. Malfunction of the fuel injection system (chapter 4).
• 3. Clogged fuel filter (chapters 1 and 4).
• 4. Malfunction in the engine management system (chapter 6).
• 5. Air leak in the intake manifold or accumulation chamber (chapters 2 and 4).

12. Violation of engine stability when driving at a constant speed

• 1. Leak in the air intake system (chapter 4).
• 2. Fuel pump malfunction (chapter 4).
• 3. Loosening of the fuel injector wiring harness connectors (chapter 4).
• 4. Malfunction of the engine control unit or sensor (chapter 6).

13. The engine stalls

• 1. Clogged fuel filter and/or presence of water and dirt in the fuel system (chapters 1 and 4).
• 2. The ignition system components are wet or damaged (chapter 5).
• 3. Malfunction of elements of the emission reduction systems (chapter 6).
• 4. Malfunction or incorrect adjustment of the spark plug gap (chapter 1).
• 5. Loss of vacuum in the fuel injection system, intake manifold or vacuum hoses (chapter 2 and 4).
• 6. Incorrect adjustment of valve clearances (chapter 1).

14. Insufficient engine power

• 1. Malfunction in the engine management system (chapter 6).
• 2. Ignition malfunction or wear (chapter 1).
• 3. Malfunction in the fuel injection system (chapter 4).
• 4. Ignition coil malfunction (chapter 5).
• 5. Brake drag (chapter 9).
• 6. Incorrect transmission fluid level in the automatic transmission (chapter 1).
• 7. Clogged fuel filter and/or presence of water and dirt in the fuel system (chapter 1 and 4).
• 8. Incorrect operation of the emission reduction systems (chapter 6).
• 9. Inequality or low compression value in the cylinders (chapter 2).
• 10. Clogged exhaust system (chapter 4).

15. Popping sounds in the engine

• 1. Incorrect operation of emission reduction systems (chapter 6).
• 2. Malfunction in the engine management system (chapter 6)
• 3. Spark plug insulator failure (chapter 1).
• 4. Malfunction in the fuel injection system (chapter 4).
• 5. Loss of vacuum in the fuel injector, intake manifold, air control valve or vacuum hoses (chapters 2 and 4)
• 6. Incorrect adjustment of valve clearances and/or valve sticking (chapter 1).

16. Knocking noises caused by too early ignition or detonation when accelerating or driving "uphill"

• 1. Incorrect grade of fuel.
• 2. Malfunction in the engine management system (chapter 6).
• 3. Malfunction in the fuel injection system (chapter 4).
• 4. Incorrect type or damage to spark plug (chapter 1).
• 5. Loss of vacuum (chapters 2 and 4).
• 6. Knock sensor malfunction (chapter 6).

17. The oil pressure warning light comes on when the engine is running

• 1. Low oil level (chapter 1)
• 2. Short circuit in the electrical circuit (chapter 12)
• 3. Malfunction of the oil pressure sensor (chapter 2).
• 4. Wear of engine bearings and/or oil pump (chapter 2).

18. The engine continues to run after the ignition is turned off

• 1. Increased engine operating temperature (chapter 3).
• 2. Malfunction in the engine management system (chapter 6).