What are the causes of insufficient cylinder pressure in a car?
2 Answers
The causes of insufficient cylinder pressure in a car are: 1. Air leakage between the cylinder head and the cylinder; 2. Air leakage between the spark plug gasket and the cylinder head or a faulty decompression valve; 3. Air leakage from the crankcase; 4. Severe wear between the piston rings and the cylinder or stuck piston rings causing air leakage. The symptoms of insufficient cylinder pressure are: 1. Excessive smoke escaping from the oil filler cap in the crankcase; 2. The lubricating oil in the oil pan becomes dirty and overheats easily; 3. A noticeable decrease in engine power while driving. The solutions for insufficient cylinder pressure are: 1. Replace the valve oil seal; 2. Replace the piston and piston rings; 3. Install a cylinder liner; 4. Replace the valve spring; 5. Replace the cylinder head gasket.
I've encountered many cases of insufficient cylinder pressure during my usual car repairs, with valve issues being the most common. When the valve seat is eroded or deformed, the seal becomes loose, and the cylinder pressure leaks directly; when the intake or exhaust valve guides wear out, the gap increases, or sludge causes sticking, the valves won't close tightly. During high engine loads, such as climbing hills or accelerating, if cylinder pressure drops, it can easily lead to power loss or shaking. Another major risk is weak or aged/broken valve springs—if the tension can't keep up, the valves close late. Some older cars, due to prolonged high-temperature operation, experience valve head erosion and deformation, which worsens if the cooling system is clogged. If you hear a hissing sound while the engine is running, check these critical points immediately—delaying too long may damage the camshaft. In short, if symptoms appear, get it inspected promptly to avoid bigger losses over minor issues.
