What are the symptoms of a faulty valve?

[LeAlivia]

Engine valve damage manifests with the following symptoms: 1. Reduced engine efficiency leading to decreased vehicle power. 2. Unstable idle or poor acceleration during engine operation. 3. Unstable cylinder operation causing black smoke emission from the engine. The causes of valve damage include: 1. Carbon buildup: Incomplete combustion and low-quality fuel lead to carbon deposits. 2. Damaged valve seals: These components prevent oil from entering the exhaust system and avoid abnormal oil consumption. 3. Valve burning: Reduced valve clearance prevents complete closure, trapping heat which leads to valve erosion by the combustion chamber's high-temperature flames.

[SanAva]

Having driven for over twenty years, I can distinctly recognize the symptoms of valve issues. The engine shakes violently, especially at idle when waiting at a red light—the entire steering wheel vibrates. Acceleration becomes noticeably weak; even with the pedal to the floor, the car struggles to pick up speed, and climbing hills feels particularly laborious. Fuel consumption spikes sharply—a full tank that used to cover 500 kilometers now barely reaches just over 400. The most frustrating part is the difficulty with cold starts; it takes multiple attempts to get the engine going in the morning. Once, I even heard metallic knocking sounds from the engine bay, which later turned out to be caused by excessive valve clearance. If blue smoke comes out of the exhaust pipe, it’s almost certainly a sign of worn valve seals burning oil. Don’t ignore these symptoms—get to a repair shop immediately for inspection.

[Willie]

When my car's valves malfunctioned last time, the most noticeable symptom was a sudden loss of power. During overtaking, the RPM would rise but the speed wouldn't increase, and climbing hills on highways was particularly strenuous. The engine warning light frequently illuminated yellow, disappearing temporarily after restarting but reappearing after a few days. Cold starts were especially difficult, particularly in winter when it took five to six seconds of turning the key to start the engine. Another obvious sign was blue smoke from the exhaust pipe, accompanied by a burnt engine oil smell, and oil stains on the ground after parking. The engine idle sound was also abnormal, resembling a metallic clattering. Fuel consumption increased distressingly, from 9 L/100km in the city to 12 L/100km. When these symptoms appear, it's advisable to immediately read the fault codes to avoid causing more severe engine damage.

[Cardoso]

As a professional frequently dealing with such issues, there are several typical symptoms of valve failure: First, abnormal engine noises, where worn valve stems produce metallic knocking sounds, especially noticeable at idle. Second, decreased cylinder pressure leading to difficulty starting, particularly when the engine is cold. Insufficient power is the most common issue, with sluggish throttle response during acceleration. Abnormal exhaust emissions are critical—blue smoke indicates faulty valve seals causing oil burning, while black smoke suggests incomplete combustion of the air-fuel mixture. Other symptoms include rough idling and a significant increase in fuel consumption. When tested with a cylinder pressure gauge, the affected cylinder's pressure will be at least 30% lower than normal. Prompt repairs can prevent valve breakage and piston damage.