Oto Engine Troubleshooting Based on Phenomenon, Operating Status

Car engine is an important device, whose main function is to convert energy (from gasoline, diesel or electricity) into kinetic energy (rotational motion) to rotate the wheels, helping the car move. According to data from the International Society of Automotive Engineers (SAE) in 2022, modern engines can convert about 20-35% of fuel energy into useful power, creating an average rotational force of 150-400 Nm to operate the transmission system and wheels.

Problems such as engine difficulty starting, uneven operation, overheating, strange noises, abnormal emissions... can cause many inconveniences, from poor vehicle performance to serious damage requiring large repair costs. According to statistics from the Vietnam Automobile Manufacturers Association (VAMA), with more than 500,000 vehicles sold in 2024, about 35% of car owners encountered engine problems in the first 3 years of use.

Understanding the warning signs, common causes and initial diagnosis will help you be more proactive in maintenance and troubleshooting, ensuring your vehicle always operates stably and safely. This article, Thanh Phong Auto will provide an overview of common engine problems, self-test and diagnostic instructions, and helpful tips for proper engine maintenance. Stay tuned!

Overview of Car Engine Problems

Automotive engine problems are issues that affect the performance and life of the engine, often caused by wear, lack of maintenance or poor quality fuel; early diagnosis and regular maintenance are extremely important to maintain stable operation and prolong engine life.

1. Common causes of engine failure

The causes of engine failures are varied, including natural wear and tear, lack of maintenance, use of poor quality fuel, or manufacturer defects. According to data from the Asian Automotive Research Center in 2023, 31.5% of engine failures are directly related to the lubrication system (oil, oil pump, oil filter), 26.8% to the cooling system (radiator, water pump, thermostat), and 22.7% to the fuel system (fuel pump, injector, fuel filter). Other causes include:

• Ignition system problems: Worn spark plugs, weak ignition coils or damaged high-voltage wires can cause the engine to be difficult to start or run erratically.
• Faulty cooling system: A clogged radiator, weak water pump or stuck thermostat can cause engine overheating.
• Clogged exhaust system: A clogged catalytic converter can reduce engine power and increase emissions.
• Faulty sensors: Faulty sensors such as the crankshaft position sensor, camshaft position sensor or mass airflow sensor can cause performance and fuel economy problems.

2. Classify engine failures based on severity

Engine failures are classified based on severity, ranging from minor issues such as reduced performance to major failures requiring engine overhaul or replacement.

• Warning Level: An illuminated oil light can indicate low oil levels, a minor problem if addressed promptly, but can cause serious damage if ignored.
• Severity: Loud knocking from the engine can indicate a bad connecting rod, a serious problem that requires an engine overhaul or replacement.

3. The importance of early diagnosis & regular maintenance

Early diagnosis and regular maintenance play an important role in maintaining performance and prolonging engine life. Early diagnosis helps detect potential problems before they become serious, minimizing repair costs. Regular maintenance includes changing the oil, air filter, fuel filter, spark plugs and checking other components, ensuring the engine runs smoothly and efficiently. 

Research shows that regular maintenance can reduce the risk of engine failure by up to 50% and extend engine life by an average of 20%.

Car Engine Self-Test & Initial Diagnosis Guide

Before taking your car to the garage, you can perform an initial engine check and diagnosis yourself to identify underlying problems. This saves you time and money, and provides useful information to the mechanic.

• Check important fluids such as engine oil, coolant, transmission oil… Observe color, level and signs of leakage and contamination.
• Check the electrical system such as battery, wires, fuses, sensors... Pay attention to corrosion, breaks, poor contact.
• Check mechanical parts such as belts, pulleys, air filters, oil filters, fuel filters, etc. Replace if signs of deterioration are detected.
• Use an OBD-II scanner to retrieve diagnostic trouble codes (DTCs) from the ECU. Look up the meaning of the codes to know exactly which part is having problems.
• Prepare necessary tools such as wrenches, screwdrivers, multimeters, pressure gauges, magnifying glasses, etc. to facilitate disassembly and measurement.

Engine Problems Difficult to Start

A car engine that is difficult to start is a condition where the car cannot start or needs to be started many times to operate, usually due to 5 main causes: weak battery, damaged spark plugs, fuel system failure, crankshaft position sensor failure or dirty idle air control valve.

• Low or dead battery:

When the battery does not have enough voltage (below 12.4V when the engine is off or below 13.5V when the engine is running), the car will be difficult to start or will only make a slight clicking sound. You can check with a voltage meter or observe signs such as dim headlights, weak horn. Charge the battery for 4-6 hours or replace it if the battery is more than 3-5 years old.

• Dirty or worn spark plugs:

Spark plugs need to create a strong enough spark (about 20,000-40,000 volts) to ignite the fuel mixture in the combustion chamber. When the spark plug is contaminated with carbon, oil or the electrode gap is worn over 1.5mm, the engine will be difficult to start, especially in cold weather below 10°C. 

Spark plugs should be checked every 30,000km and replaced as a set every 60,000-100,000km depending on the type of spark plug (iridium, platinum or copper).

• Fuel system malfunction:

A clogged fuel filter (after 40,000-60,000km), low fuel pump pressure (below 40-45 PSI for fuel-injected engines), or dirty injectors will result in insufficient fuel to burn. Signs include: engine jerking, unusual noises from the fuel pump, or the vehicle starting and then stalling. 

The optimal solution is to clean the fuel system with a specialized solution, replace the fuel filter according to the maintenance schedule, and check the fuel pump pressure.

• Crankshaft position sensor (CKP sensor) failure:

This sensor measures the rotational speed and precise position of the crankshaft, sending signals to the ECU to control ignition and fuel injection. When this sensor fails, the vehicle will have difficulty starting, the check engine light will come on (error codes P0335-P0338), and the engine may suddenly stall. 

Check with OBD2 diagnostic machine and replace the sensor if it is found to be faulty. The life of this sensor is usually 80,000-120,000km depending on usage conditions.

• Idle air control valve (IAC valve) dirty or damaged:

The IAC valve regulates the amount of air entering the engine when idling, maintaining a stable engine speed of 700-900 rpm. When this valve is contaminated with carbon, oil or damaged, the vehicle will be difficult to start, stall immediately after starting or have an unstable idle speed. 

You can clean the valve with a specialized cleaning solution or replace it if it has been used for more than 80,000km. The simple cleaning process includes: remove the valve, spray with cleaning solution, dry and reinstall.

Engine Running Unevenly, Shaking

Engine misfires and jerks are signs of an engine not running smoothly, possibly due to one or more cylinders not working properly. Some common causes include:

• A dirty or worn spark plug does not produce a strong enough spark to ignite the fuel mixture in the cylinder. Inspect and replace the spark plug if necessary.
• A weak ignition coil does not supply enough voltage to the spark plug, resulting in weak or no spark. Inspect and replace the ignition coil if necessary.
• Dirty or clogged injectors do not spray fuel evenly into the cylinders. Clean or replace injectors.
• Air leaks in the intake system can alter the air/fuel mixture ratio in the cylinder, resulting in incomplete combustion. Check and repair leaks in the intake system.
• Low cylinder pressure can be caused by worn piston rings, leaking valves or damaged cylinder head gaskets. Check cylinder pressure and repair if necessary.

Engine Overheating

Engine overheating occurs when the engine temperature exceeds 100-110°C (safe level is 80-90°C), causing deformation and serious damage to parts such as seals, gaskets and cooling systems, leading to reduced engine life. Some common causes include:

• Lack of coolant is the cause of 40% of cases of engine overheating. Check the coolant level in the reservoir to make sure it is between the MIN and MAX lines, and add specialized coolant if it is lower than the MIN line. Note that only add more when the engine is completely cool to avoid thermal shock. 
• A faulty water pump does not circulate coolant through the engine quickly enough, causing the engine to overheat. Check and replace the water pump if necessary.
• A thermostat that is stuck in the closed position prevents coolant from circulating through the radiator, causing the engine temperature to rise rapidly after only 5-10 minutes of operation. Signs of a faulty thermostat include a high engine temperature but the radiator hose remains cold. Replacement costs range from 300.000 to 800.000 VND depending on the vehicle type and takes about 1-2 hours to complete.
• The radiator is clogged with dirt, rust and minerals that accumulate after about 40.000-60.000 km, reducing the heat dissipation capacity by 30-50%, leading to engine overheating. To handle this, it is necessary to flush the cooling system with a specialized solution, replace the coolant or replace the radiator if it is severely damaged. The flushing process should be performed every 30.000 km to maintain cooling efficiency.
• A non-functioning cooling fan (due to a faulty control relay, blown fuse or weak fan motor) reduces the air flow through the radiator by 70%, causing the engine to overheat, especially when the vehicle is stopped or moving slowly in urban areas. Check the fan by observing when the engine reaches operating temperature (about 85-90°C) – the fan should activate automatically. If it does not operate, the fuse, relay and fan motor should be checked for repair or replacement.

Strange Noise From Engine

Strange engine noises can be a sign of a variety of problems, from minor to serious. Pinpointing the exact source of the noise can help you diagnose and fix the problem more effectively. According to the American Society of Automotive Technicians (ASE) in 2023, accurately identifying sounds (such as metallic knocking, high-pitched whining, low-pitched buzzing) can help identify 75% of problems before they become serious, saving an average of 65% on repair costs.

Some common strange noises and their causes include:

• Knocking can be caused by a number of things, including using low-octane fuel, overheating the engine, or wearing out internal engine parts. Severe knocking can cause damage to the pistons, connecting rods, and crankshaft.
• Squealing noises are usually caused by a slipping belt. Check and adjust belt tension, or replace the belt if worn or cracked.
• Ticking can be caused by a leaking valve, or worn parts in the valve system. Check and adjust the valve clearance, or replace worn parts.
• Whining noises can be caused by a faulty power steering pump, or worn bearings in the engine. Inspect and replace damaged parts.
• Popping noises from the exhaust can be caused by a lean air/fuel mixture, or a problem with the ignition system. Check and repair the fuel and ignition systems.

Abnormal Emissions

Abnormal emissions are toxic gases emitted from the engine with unusual color, odor or composition, signaling serious technical problems in the fuel combustion system or engine. 

According to research from the Vietnam Register in 2024, abnormal emissions increase fuel consumption by 25-30%, reduce engine performance by 15-20% and can contain toxic concentrations 5 times higher than the current Euro III standard in Vietnam.

Some common types of abnormal emissions and their causes include:

• Black smoke is usually caused by an air/fuel mixture that is too rich, meaning there is too much fuel relative to the amount of air. This can be caused by leaking injectors, a faulty mass air flow sensor (MAF sensor), or a faulty fuel pressure regulator.
• White smoke can be caused by water entering the combustion chamber, usually due to a damaged cylinder head gasket, or a cracked cylinder head. White smoke can also be caused by oil entering the combustion chamber, usually due to worn piston rings, or a damaged valve seal.
• Blue smoke is usually caused by oil entering the combustion chamber, usually due to worn piston rings, or damaged valve seals.
• A gasoline smell in the exhaust can be caused by a leak in the evaporative emission control system (EVAP system), or a saturated charcoal canister.

Check Engine Light

The Check Engine Light (CEL) is a warning light on your vehicle's dashboard that illuminates when the engine control unit (ECU) detects a problem with the engine or related systems. The CEL may stay on, flash, or stay on and off. 

When the CEL light is on, you should take your car to a garage to have the problem checked and diagnosed. You can also use an OBD-II code reader to read the error codes stored in the ECU, which can help determine the cause of the problem. However, it is important to note that the error codes only provide a clue, and accurate diagnosis often requires specialized knowledge and experience.

Periodic Maintenance of Car Engine

Regular maintenance is the process of checking and replacing parts on a scheduled basis to maintain optimal performance and prolong engine life. Performing regular maintenance reduces the chance of unexpected breakdowns by 70%, saves 15-30% on fuel costs, and ensures driver safety. Regular maintenance includes the following tasks:

• Regular oil and filter changes help remove dirt and maintain the oil's lubricating ability, reducing friction and wear on engine parts. Oil change intervals are usually between 5.000 km and 10.000 km, depending on the type of oil and operating conditions.
• Replace the air filter: A dirty air filter reduces the amount of air flowing into the engine, resulting in reduced performance and increased fuel consumption. Regularly replacing the air filter helps ensure that the engine receives enough clean air. The air filter replacement interval is usually between 10.000 km and 20.000 km, depending on operating conditions.
• Replace fuel filter: A dirty fuel filter reduces fuel flow to the engine, resulting in reduced performance and difficulty starting. Changing the fuel filter regularly helps ensure that the engine receives enough clean fuel. Fuel filter replacement intervals typically range from 20.000 km to 40.000 km, depending on fuel quality.
• Spark Plug Replacement: Worn spark plugs reduce the ability to ignite, leading to reduced performance, increased fuel consumption and abnormal emissions. Regular spark plug replacement helps ensure efficient engine ignition. Spark plug replacement intervals typically range from 30.000 km to 50.000 km, depending on the type of spark plug.
• Check and adjust valve clearance: Incorrect valve clearance can reduce engine performance and cause strange noises. Checking and adjusting valve clearance periodically helps ensure that the valves open and close at the correct time.
• Inspect and replace belts: Worn or cracked belts can cause problems with your steering, cooling, or air conditioning systems. Regularly inspecting and replacing belts helps ensure these systems operate properly.
• Check the cooling system: Check the coolant level, radiator, water pipes and thermostat to ensure the cooling system is working effectively, avoiding engine overheating.
• Exhaust system check: Check the exhaust pipe, catalytic converter and related sensors to ensure the exhaust system is operating effectively, reducing emissions and noise.

Be sure to perform all maintenance items recommended by the manufacturer based on time or distance traveled.

FAQ – Frequently Asked Questions

1. What is the typical range of engine repair costs?

Depending on the extent of damage and the type of engine, repair costs can range from a few million to tens of millions of dong. Replacing a new engine can cost hundreds of millions of dong.

2. What types of insurance can cover engine repairs?

Car insurrance (comprehensive insurance) often includes the cost of engine repairs if damage is caused by an accident or natural disaster.

3. Should I use genuine replacement parts or OEM replacement parts?

Genuine parts ensure the best quality and compatibility, but are more expensive. OEM parts are cheaper and of the same quality. However, you should buy from reputable suppliers. See the article now: Distinguish between genuine, OEM, and Aftermarket auto parts Simplest, most accurate.

4. What types of additives can help improve performance and extend engine life?

Some common additives include combustion chamber cleaners, lubricants, and octane enhancers. However, you should consult an expert before using them.

5. When should you replace the engine instead of overhauling it?

If the engine is too old (over 10 years) or the cost motor overhaul If the engine value exceeds 70% of the new value, it should be considered for replacement to ensure performance and reliability.

6. How to check and change engine oil properly at home?

Use the dipstick to check the oil level and color. If the oil is black or the oil level is lower than 6 liters/100km, it needs to be checked again. Refer to the article 4 Notes when changing car engine oil in HCM safely.

7. When buying a used car, how can I thoroughly check the engine condition?

when the buy used cars, it is important to check the engine condition carefully to avoid buying a poor quality car. The inspection steps include:

• Check vehicle maintenance and repair history.
• Observe the color of the exhaust smoke, listen to the engine sound when starting and accelerating.
• Check the oil level and color of the engine oil.
• Check out the signs of oil leak, cooling water.
• Use OBD-II diagnostic device to check for faults.
• Take the car to a reputable garage for a comprehensive check.

8. Which garage repairs/maintains car engines with good reputation and good prices in Ho Chi Minh City?

Car repair, maintenance and care services at Thanh Phong Auto is one of the most prestigious and high-quality services in Ho Chi Minh City. With a team of skilled technicians, modern equipment and professional working process, Thanh Phong Auto is confident in bringing customers the best service experience.

Some outstanding advantages of services at Thanh Phong Auto:

• Our team of experienced, well-trained technicians are always updated with the most advanced repair techniques.
• Fully equipped with modern specialized machinery and equipment such as diagnostic machines, tire pressure testing equipment, etc. to help diagnose accurately and thoroughly repair problems. See the article now: Car pressure sensor – Which type is good & what to note.
• Using genuine spare parts and components, ensuring the best quality and compatibility with each vehicle model.
• Professional, standard 6-step repair and maintenance process helps optimize service time and quality.
• The workshop space is spacious, airy, clean, ensuring vehicle safety during repair.
• Dedicated and thoughtful customer service. Enthusiastic advice helps customers understand the condition of the vehicle and make the most appropriate choice.
• Competitive, transparent prices, no additional costs. Many attractive promotions.

With the above outstanding advantages, Thanh Phong Auto deserves to be a reliable destination for every car owner when needing care and maintenance services for their "beloved car".

Hopefully the above article has provided you with useful knowledge on how to recognize and handle common car engine problems. Be proactive in checking and maintaining your car regularly so that the “heart” of your beloved car is always healthy, accompanying you on every road.