Fault: fault diagnosis: check the fuel injector and spark plug, and clean the nozzle. Both are normal. It is normal to test the pressure of each cylinder. After discussion and analysis, since the problem of engine overhaul, it is possible that the piston ring is not properly installed, and it will leak in the hot car. So they decided to remove the engine, remove the cylinder head and pull out the piston, and found that the connecting rod bush was pulled. Cylinder head decomposition found that the second cylinder valve was not easy to pull out, the valve rod slightly bent, and the eccentric bush was pulled. The reason is that the repairman did not twist the crankshaft and connecting rod screws in accordance with the standard torque. When the engine is installed, the bearing bush is too tight due to the heat, breaking the timing gear pin and breaking the belt, resulting in engine failure. Later, when the timing pin was installed, the valve was normally opened and closed because of the second cylinder inlet valve bending, and the engine worked normally. After the hot car, the valve stem is expanded and jammed. The second cylinder leaks, the pressure is not enough, the engine does not work and the engine is jitter.