If your car exhaust producing black smoke after started, feeling engine power loss during driving, increased fuel consumption, it might be due to insufficient pressure in the cylinder. A cylinder without sufficient pressure normally cause by below reasons:
1. Piston or piston ring worn out after grinding with cylinder wall, causing the clearance become greater.
2. Piston ring stuck at the ring groove after worn out due to greater clearance and drop in rebouncing force.
3. Burnt cylinder gasket, loosen screw on the cylinder head cover, deformed cylinder or cylinder head cover, causing poor seal.
4. Poor seal between the valve and seat, clearance on the valve is too small, broken valve spring or insufficient rebouncing force.
5. Leakage between the spark plug gasket seal and the valve cover. Broken, contaminated or even forgot to install the spark plug gasket seal will cause leakage between the spark plug gasket seal and valve cover, resulting in insufficient compression pressure in the cylinder.
6. If confirmed there is insufficient pressure in the cylinder, suggest to proceed to repair at workshop as soon as possible.
Suggest to diagnose at workshop, usually the keypoints of diagnose are:
1. Check the seal between valve and valve seat, proceed with grinding if necessary or replace with a new unit.
2. Check the worn level of the piston ring, adjust or replace piston ring if necessary.
3. Measure the worn level of cylinder liner, replace if necessary.
4. Check if the valve spring is broken, or the rebounce force has dropped significantly.
5. Check the valve gasket if there is leakgage, replace if necessary.
6. Check if the spark plug gasket seal is aged, replace if necessary.