What are the problems that occur in different positions of the engine?

The car engine is a complex system, and when it malfunctions, it usually sends us a "distress signal". We can preliminarily determine the problem by "looking, listening, feeling, and checking".

Below, I will categorize engine abnormalities into several types and explain their possible causes:

Category 1: Startup and Idle Issues

1. Difficulty or inability to start

Symptoms: The starter does not turn, the starter rotates but the engine does not ignite, and multiple attempts are required to start.

Possible reasons:

Circuit issue (ensure ignition):

Battery: Loss of power or damage (most common). Manifesting as a weak starter or only hearing a "click" sound.

Starter: It has a malfunction.

Ignition coil/spark plug: Aging or malfunction, resulting in no spark or weak spark.

Oil circuit issue (ensuring fuel injection):

Fuel pump: not working, resulting in the inability to deliver fuel to the engine.

Fuel injector: clogged or leaking.

Fuel filter: clogged.

Air circuit issues (ensuring compression):

Engine timing: The belt or chain teeth jump, causing the valve opening and closing time to be misaligned.

Insufficient cylinder pressure: It may be due to poor sealing of valves or piston rings.

2. Unstable idle, shaking or stalling

Symptoms: When waiting for a red light, the tachometer pointer fluctuates up and down, the car body shakes significantly, and even automatically stalls.

Possible reasons:

Carbon deposition problem: Excessive carbon deposition on the throttle valve, intake duct, and fuel injectors affects the intake and injection quantities.

Ignition system issue: A spark plug or ignition coil malfunction causes a "cylinder shortage" (one cylinder not working).

Sensor malfunction:

Air flow sensor or intake pressure sensor: giving incorrect intake signal to the computer.

Oxygen sensor: unable to accurately monitor exhaust gas, resulting in air-fuel ratio imbalance.

Vacuum leakage: There are cracks or detachment in the intake pipeline (especially the rubber hose), causing unmeasured air to enter.

Category 2: Power and acceleration issues

1. Weak acceleration and slow acceleration

Symptom: Stepping on the accelerator deeply, but the speed increases slowly, feeling "fleshy".

Possible reasons:

Poor intake: The air filter is too dirty and clogged.

Insufficient fuel pressure: aging fuel pump or clogged fuel filter.

Poor exhaust: The three-way catalyst is blocked and the exhaust gas cannot be discharged.

Turbocharger: malfunction (for turbocharged engines).

Clutch slippage (for manual transmission): The engine speed increases rapidly, but the vehicle speed is not fast.

2. Acceleration jerks and jolts

Symptom: When accelerating, the car rushes back and forth and is not linear.

Possible reasons:

Ignition system: Poor performance of spark plugs or ignition coils, resulting in misfiring at high loads.

Fuel system: clogged or leaking fuel injectors, irregular fuel injection.

Transmission issue: Malfunction of solenoid valves, clutch plates, or torque converters in automatic transmissions.

Category 3: Abnormal noise and noise

Symptoms: Abnormal sounds such as knocking, hissing, and clattering are heard from the engine compartment.

Possible reasons:

Dada sound: It is usually the sound made by the hydraulic top cylinder due to insufficient oil pressure or wear and tear. It is obvious during cold start, and it is normal for it to decrease after heating up.

Metal 'knocking' sound (called rod): usually occurs during acceleration. It may be due to the use of low-grade gasoline causing detonation, or wear of piston pins and connecting rod bearings.

Squeak "scream: usually caused by the aging and slipping of belts (generator, air conditioning compressor belts).

The "click" sound increases with the speed: it may be due to severe wear of the valve or valve tappet.

Category 4: Abnormal exhaust

Symptom: Abnormal color of smoke emitted from the exhaust pipe.

Possible reasons:

Black smoke: The mixture is too rich and the fuel is not fully burned.

Reason: Air filter blockage, fuel injector leakage, sensor (such as oxygen sensor) malfunction.

Blue smoke: burning engine oil.

Reason: Wear of piston rings, aging of valve oil seals (obvious blue smoke during cold start), and damage to turbocharger oil seals.

White smoke (large and continuous): Water enters the combustion chamber, usually coolant.

Reason: The cylinder gasket is damaged (flushing gasket), causing coolant to enter the cylinder.

Category 5: Water Temperature and Warning Lights

1. The engine water temperature is too high

Possible reasons:

Coolant: Leakage or insufficient.

Thermostat: unable to open properly, resulting in the inability to perform large cycles.

Cooling fan: Motor or relay failure, not rotating.

Water pump: damaged, causing the coolant to not circulate.

2. The engine malfunction light is on

Explanation: This is a signal detected by the engine electronic control system (ECU) as abnormal.

Possible reasons: The range is extremely wide, from simple fuel tank cap not tightened (causing leakage in the evaporation system) to severe knock sensor failure and low efficiency of the three-way catalyst. A professional diagnostic computer must be used to read the fault code in order to determine the specific problem.