What's wrong with the idle speed of the 465 engine?

The reasons that cause the 465 engine to rise and fall at idle speed are: 1, too much carbon deposit on the throttle; 2. Leakage of intake manifold or various valves. This fault directly affects the quality and combustion effect of fuel mixture. Parts that may leak, such as intake manifold, vacuum tube, activated carbon canister valve, exhaust gas recirculation (EGR) valve and positive crankcase ventilation (PCV) valve, need to be overhauled one by one. 3. Valve timing failure. Incorrect valve timing, incorrect installation of timing belt, excessive carbon deposition in intake and exhaust valves, broken valve spring, etc. , the air intake of each cylinder is different, and the idle speed will be unstable; 4. The three-way catalytic converter is blocked. The blockage of three-way catalyst not only leads to unstable idle speed, but also leads to insufficient power; 5. The fuel injector is faulty. For example, the nozzle atomization is not good, and the nozzle is blocked. , the nozzle needs cleaning; 6. Fuel pressure is too low. Mainly check whether the fuel filter, fuel pump and other components are blocked and whether the oil pipe is deformed.