The instability of the diesel engine speed refers to the phenomenon of trembling, swinging and rotating speed of the engine when the throttle is in a certain position. To eliminate erratic rotating speed, check and eliminate from the following four steps: Step one: Check or replace the fuel tank to the high pressure oil inlet screw This section of the oil seal at the joint, cleaning or replacement of the diesel filter and filter The small filter in the screw is replaced with a trachoma or a tubing with a broken inner wall. Ensure the smooth flow of low-pressure oil, so that there is no air and plugging. Step 2: Check and adjust the valve clearance and check whether the valve stem is bent to ensure that the gas distribution phase meets the specified requirements. The third step: focus on checking the cylinder pad, piston ring, the difference between the weight of each cylinder's piston connecting rod group, the wear condition of the valve camshaft and the tappet body assembly, check the connecting rod's buckling condition, etc. to ensure the parts The assembly quality of the assembly meets the regulatory requirements. Step 4: If the fault still cannot be eliminated, you should suspect the injector assembly and the reason for the fuel injection pump assembly. It should be adjusted and corrected by professional and technical personnel to ensure the normal operation of the fuel supply system. In general, if the instability occurs at low speeds, check the nozzles; if the speed is unstable, check the engine; if it is unstable at high speed, check the oil pump.