Legally reviewed by: Jessica Anvar Stotz, JD, MBA

When it comes to your vehicle, the engine is its heart. Recognizing the signs of a bad engine can save you from a costly repair bill or even total engine failure. Your vehicle will show either minor or major signs signaling that its engine is about to fail before it does.

signs of engine failure

Top 10 Signs of Engine Failure to Look Out For

1. Excessive SmokeVisible smoke coming out from the exhaust in unusual amounts.
2. Strange NoisesUnusual sounds like knocking, popping, or hissing coming from the engine.
3. Loss of PowerDifficulty in maintaining speed, especially on inclines or when carrying heavy loads.
4. Poor Fuel EfficiencyYour vehicle is consuming more fuel than usual.
5. Engine StallingYour vehicle frequently stops running and needs to be restarted.
6. OverheatingThe temperature gauge reads higher than normal or the vehicle feels hot.
7. Oil LeaksPuddles of oil under the vehicle or oil stains on other parts of the engine.
8. Check Engine LightThe check engine light on your dashboard is illuminated.
9. Bad OdorsUnusual smells coming from the engine or exhaust.
10. VibrationsUnusual shaking or vibrations when the engine is running.

1. Excessive Smoke

One of the most visible signs of a bad engine is the presence of excessive smoke from the exhaust. This symptom is not only alarming but can also provide valuable insight into the nature of the underlying issue:

  • Blue Smoke: If you notice blue smoke, it’s a clear indication of oil burning in the combustion chamber. This could be due to worn-out seals or rings, which allow oil to seep into the combustion chamber and get burned along with the fuel.
  • White Smoke: White smoke, on the other hand, could signify a coolant leak. This happens when the coolant enters the combustion chamber, usually due to a cracked cylinder head or a blown head gasket.
  • Black Smoke: If you start seeing black smoke that doesn’t clear as the engine warms up, it could mean the air filter has been clogged up. A simple replacement might do the trick. However, if the problem persists, it’s likely that the air-to-fuel ratio is off balance. This could be due to a malfunctioning sensor or a problem with the fuel injection system.

In any case, excessive smoke is a sign that your vehicle needs immediate attention. You should address these vehicle issues promptly to prevent further engine damage and ensure the longevity of your vehicle.

2. Strange Noises

One of the most common signs of engine problems is the presence of unusual noises. These sounds can range from knocking and popping to hissing, each indicating a different potential issue.

  • Knocking Sounds: A knocking sound from your engine often suggests that the engine bearings are worn. This could be due to low oil pressure or poor-quality oil, which fails to lubricate the engine effectively.
  • Popping Sounds: Popping sounds can be a sign of a malfunctioning ignition system. This could be due to a variety of issues, from a simple need for a tune-up to a serious problem like a faulty spark plug or ignition coil.
  • Hissing Sounds: A hissing sound is often indicative of a leak, either in the cooling system or the vacuum. This could lead to performance issues and overheating, potentially causing severe engine damage.

Now, if you hear a grinding noise, this is likely related to your vehicle’s braking system rather than the engine. This sound typically means your front brake pads are getting worn away every time you hit the road.

Once the last bit of the front brake pad is gone, the metal backing plate will clamp directly onto the brake disc–significantly reducing the car’s braking effectiveness. We strongly advise against driving your car when things get this bad.

3. Loss of Power

One particularly alarming sign of a bad engine is a noticeable loss of power. This symptom can manifest in several different ways, each indicating a potential issue with your vehicle’s engine:

  • Struggling to Maintain Speed: If your car struggles to maintain its speed, especially on inclines or when carrying heavy loads, it could be a sign of engine trouble. This could be due to a variety of issues, including a clogged exhaust system, a failing fuel pump, or worn-out spark plugs.
  • Failing to Accelerate: Similarly, if your car fails to accelerate smoothly or quickly, this could be a sign of a bad engine. This could be due to issues with the fuel system, such as a clogged fuel filter or a malfunctioning fuel injector, which prevent the engine from receiving the necessary amount of fuel.
  • Catalytic Converter Issues: A failing catalytic converter can also cause a loss of power. The catalytic converter is responsible for converting harmful exhaust gases into less harmful substances. If it’s failing, it can become clogged, restricting the flow of exhaust and causing your engine to run inefficiently and lose power.

Please note that these are just signs and symptoms. If you notice any of these, it’s important to have your vehicle inspected by a professional mechanic to diagnose and fix the issue. Ignoring these signs could lead to total car engine failure.

4. Poor Fuel Efficiency

A sudden drop in fuel efficiency can be a sign of engine problems. Bad fuel efficiency can stem from a range of factors, encompassing everything from a clogged air filter inhibiting optimal airflow, to a faulty sensor providing inaccurate data to the engine’s control unit. There exist numerous malfunctions that can lead your engine to consume excessive fuel, such as:

  • Blocked or faulty injectors
  • Bad spark plug
  • Fuel leaks
  • Faulty air sensors

5. Engine Stalling

If your engine keeps stalling while your vehicle is idle, engine failure could be a possible cause. If your engine consistently stalls while your vehicle is idling, it could be a harbinger of impending engine failure. The need to repeatedly restart your vehicle while it is idling could indicate an issue with fuel delivery.

One potential culprit of engine problems could be a failing sensor. Modern vehicles rely on a variety of sensors to regulate engine performance, and a faulty one can disrupt the delicate balance needed for smooth operation. For instance, a failing mass airflow sensor or oxygen sensor can cause the engine to stall at idle.

Fuel System Issues can also cause engine stalling–this could be due to a clogged fuel filter, a failing fuel pump, or issues with the fuel injectors. Each of these components plays a crucial role in delivering the right amount of fuel to the engine, and any disruption can lead to stalling.

6. Overheating

Symptoms of engine damage from overheating can include:

  • High Temperature Gauge Reading: One of the first signs of an overheating engine is a high reading on your temperature gauge. This indicates that your engine’s temperature is above its optimal operating range and needs immediate attention.
  • Steam: Steam or smoke coming from under the hood is another clear sign of overheating. This usually happens when the coolant boils over and evaporates due to the excessive heat.
  • Sweet Smell: A sweet, maple syrup-like smell is often associated with leaking coolant. The coolant has a sweet, somewhat fruity smell, and when it leaks and gets heated by the engine, you might be able to smell it.

Running an engine that’s overheating can lead to a host of problems. One of the most severe consequences is a warped cylinder head. The extreme heat can cause the metal of the cylinder head to warp, leading to a poor seal with the engine block. This can allow coolant to leak into the combustion chamber, further exacerbating the overheating problem and potentially leading to complete engine failure.

7. Oil Leaks

The presence of oil spots under your car or a noticeable decrease in oil level could be indicative of an oil leak, one of the more serious engine problems. If you notice dark spots under your parked car or find that your oil level is consistently low even after topping up, there could be an oil leak.

Running your engine without sufficient oil can lead to severe damage. The lack of adequate lubrication can cause increased friction among the engine components, leading to wear and tear, overheating, and in severe cases, complete engine failure. If you are wondering how to tell if the engine is damaged from no oil, there are a few telltale signs. A persistent knocking sound from the engine, overheating even under normal driving conditions, or the oil pressure light illuminating on your dashboard are all signs of potential engine damage due to low oil.

8. Check Engine Light

The check engine light, typically situated behind the steering column, serves as a crucial indicator of potential issues with your vehicle. Its illumination is a clear communication from your vehicle’s onboard diagnostic system that there could be a problem potentially involving the engine:

  • Steady Illumination: A steady light is a sign that you should schedule an appointment with a mechanic at your earliest convenience. While the issue might not be urgent, it’s important not to ignore this warning.
  • Blinking Light: If the check engine light is blinking, this is an immediate call for concern. This usually indicates a severe engine misfire, permitting unburned fuel into the exhaust system. There, it can quickly raise the temperature of the catalytic converter to a point where damage is likely, necessitating expensive repairs.

Regardless of whether the light is steady or blinking, you should get your vehicle checked immediately if you notice a check engine light. Prompt attention to the check engine light can prevent more serious damage to your vehicle and help diagnose the problem, along with identifying any other potential issues.

9. Bad Odors

Distinctive smells can often indicate engine problems. The scent of burning rubber or hot oil could point to a leak, an overheating engine, or a worn-out part. A sweet smell, akin to maple syrup, is particularly noteworthy. This aroma, noticeable when the engine is warm or just after shutoff, is likely due to a coolant leak.

The source of an unusual smell can help diagnose the issue. If the scent is stronger outside the car, check the radiator and radiator cap for leaks. Inside the cabin, the smell could indicate a faulty heater core or issues with an intake manifold gasket.

10. Vibrations

If your car is exhibiting unusual vibrations or shaking, it could be a clear indication of engine problems. This unsettling behavior could stem from a variety of issues:

  • Engine Misfire: One common cause is an engine misfire, which can create a noticeable jittery sensation. Misfires often result from faulty spark plugs, which disrupt the engine’s normal firing sequence.
  • Worn-Out Engine Mount: A worn-out engine mount, which is designed to secure the engine and absorb vibrations, can also lead to noticeable shaking if it’s failing.
  • Suspension Issues: Problems with the suspension system can also cause your car to shake or vibrate. While not directly an engine problem, it can affect the overall performance and comfort of your vehicle.

If you notice excessive vibrations, particularly in the engine, a faulty spark plug could be the culprit. Faulty spark plugs can cause the engine to misfire, leading to noticeable vibrations. While replacing the spark plug can often rectify this issue, if left unchecked, it could lead to additional engine damage.

Please note that these are just possible engine failure symptoms. If you notice any of these, you should have your vehicle inspected by a professional mechanic to diagnose and fix the issue. Ignoring these signs could lead to complete car engine failure or other serious issues.

engine failure signs

Engine Failure and Lemon Law

If you are or have encountered repeat warranty repairs with your vehicle related to engine, there is a chance that your car could be a lemon. A ‘lemon’ is a term used to describe a vehicle that, due to manufacturing defects, fails to meet the standards of quality and performance set forth by the manufacturer.

Consumers who purchase or lease a lemon vehicle are protected by the ‘lemon laws’. These laws provide consumers with certain remedies, which may include a full refund, a replacement vehicle, or cash compensation as a result of the defective vehicles.

Engine problems are among the most frequently cited symptoms in lemon law cases against auto manufacturers. If you are dealing with repeat engine issues in your vehicle that the manufacturer has been unable to resolve within repeat repair visits, there is a chance that your vehicle qualifies as a lemon and you may be entitle to a refund or cash compensation.

Get Help from the Lemon Law Experts!

If you suspect that you purchased or leased a lemon vehicle in California, the Lemon Law Experts can help. Our team has assisted thousands of consumers across the state of California recover millions of dollars in compensation for their lemon vehicles against a range of auto manufacturers.

As California’s leading lemon law firm, we hold the expertise and experience to secure the best possible outcomes for our clients.  Contact us today to learn more.