The mileage is over 260 thousand km, and the 2005 TOYOTA Prado assembled for the 1 GR-FE engine. Customer response: the car engine jitter abnormal noise and accelerated weakness. Fault analysis: vehicle inspection, oil, cooling fluid normal, starting the engine, in the left cylinder head, the "gear gear", the sound, engine jitter serious. The left valve chamber cover is removed and checked. It is found that the first bearing bush on the intake camshaft side has a screw loose, and there is a 1cm out of it. At that time, it was thought that the screw was fastened and the vehicle trial run was started again after finding the cause. The abnormal noise has been relieved, but the engine jitter has not changed. The cylinder test shows that the 3 cylinders on the left side do not work. There is no way to open the top cover and check the engine again. It is found that the intake camshaft is broken in the second axle neck. The removal of the left cylinder head revealed that the first bearing bush had locked the intake camshaft and pulled the camshaft due to inertia. The shaft of the camshaft is caused by bad lubrication, the oil oil level is normal, the driver reflects that the oil indicator light is not found, the customer insists on finding the reason to repair, open the oil bottom shell, find the oil bottom shell is all oil, the filter has been covered by the mud, this is the problem. Talking with customers, the customer said that just a few days ago, he had just done a job of removing oil sludge. The oil sludge in the oil pan should be stored in the oil pan when cleaning the sludge inside the engine. This is the fault caused by the insufficient oil pressure of the oil pump. Troubleshooting: remove the engine, thoroughly clean the engine, replace the cylinder head and solve the problem. Failure enlightenment: for the old cars with more mileage, it is not recommended to do some deep maintenance. Fault comment: old cars should be cautious when doing maintenance work. We should not blindly pursue the output value of the bicycle, but ignore the technical condition of the vehicle itself.