What are the symptoms of insufficient cylinder pressure in a car engine?

[LePeter]

Symptoms of insufficient cylinder pressure in a car engine: It can cause difficulties in engine starting, insufficient power, vibration during operation, increased fuel consumption, and failure to meet exhaust emission standards. Normally, the cylinder pressure measured by the starter should be above 8 kg. Causes of insufficient cylinder pressure in the engine: 1. Severe wear of piston rings, leading to reduced sealing effectiveness; 2. Scratches, unevenness, or abnormal wear on the cylinder walls; 3. Poor sealing of the valve seat or spark plug seat; 4. Damage to the cylinder head gasket. The function of the cylinder head gasket is to keep adjacent cylinders independent of each other. If the cylinder head gasket is damaged, the two cylinders may become connected, naturally resulting in insufficient cylinder pressure. Additionally, damage to the cylinder head gasket can also lead to the mixing of engine oil and coolant, which may then enter the cylinder and burn.

[Ariel]

Recently, I encountered this frustrating issue with my car. Starting the engine was particularly difficult, and it failed to ignite several times, as if it hadn't 'eaten enough.' At idle, the steering wheel shook violently, and the entire car vibrated like a massage chair. On the highway, the throttle felt sluggish, and when climbing a hill, the tachometer jumped wildly but the speed just wouldn't increase. What's even more annoying is that the fuel consumption suddenly skyrocketed—I had to refuel after just 300 kilometers on a full tank, and there was a pungent burnt smell from the exhaust. Last week, after an inspection, it was confirmed to be low cylinder compression. The mechanic said if I kept delaying, it might require a major engine overhaul.

[VonMaddox]

With 20 years of auto repair experience, I've seen countless vehicles with low cylinder compression. The most common symptom is difficulty starting when cold, especially noticeable in winter—the battery is fine but the starter just cranks without firing up. At idle, the tachometer needle dances like it's doing the tango, and the car shakes so badly it scares passengers. The power loss is painfully obvious—overtaking on flat roads becomes a struggle, let alone climbing hills. Blue smoke frequently puffs from the exhaust, with fuel consumption 20-30% higher than normal. The most troubling part? That metallic knocking sound during hard acceleration indicates detonation. Left untreated, this will eventually destroy piston rings and valves.

[MacSpencer]

I'm someone who loves tinkering with cars, and insufficient cylinder pressure most noticeably makes the engine feel weak. When starting a cold engine, it takes five or six attempts to fire up, and after warming up, the idle speed fluctuates erratically. It's especially obvious while driving—stepping on the gas for overtaking feels sluggish, and climbing hills lacks power. The exhaust emits black smoke, and fuel consumption is alarmingly high. Once during a long trip, the power suddenly cut out for a few seconds, which gave me a cold sweat. Upon inspection, the spark plugs were all covered in carbon deposits, and the pressure gauge showed that one cylinder's pressure was only half the normal value. The mechanic said the most likely issue was valve leakage and warned that if not repaired soon, it could lead to cylinder scoring.