Q: The causes of unstable engine idle speed and troubleshooting methods?
A: The engine idle speed is unstable in the form of idling, fast and slow, or vibration.
(1) Cause
① Air in the oil circuit.
② Poor oil supply in the low pressure oil circuit.
③ Improper adjustment of idle speed stabilizer.
④ Poor atomization of fuel injector.
⑤ Uneven oil supply from injection pump.
(6) Excessive wear of parts such as the pins of the engine governor connecting rods.
(2) Diagnosis and treatment method
When diagnosing the unstable idle speed, it should be analyzed and judged according to the length of time the engine has been used and the degree of maintenance of the engine.
① First of all, you should check whether the oil supply of the low-pressure oil circuit is smooth, check _ whether the filling of diesel fuel meets the requirements, whether the maintenance of the car engine is timely, otherwise it should be cleaned or maintained and replaced.
② If the engine has not been used for a long time or the tank oil is not replenished in time, a small amount of air seeps into the oil circuit and should be exhausted.
③ If the engine has been used for a long time, the injection pump has been debugged several times without checking the wear of the engine governor, when debugging, pay attention to test the speed control components, throttle lever parts of the connections are not too much wear phenomenon. Otherwise, the parts should be replaced or welding repair process. Welding repair of rotating parts, should pay attention to the symmetry of the quality to ensure balance.
④ Idle speed is unstable and accompanied by vibration, is due to the injection pump oil supply unevenly caused by the available cylinder by cylinder oil break method to check. If the broken cylinder does not cause the speed change, it means that the cylinder is not enough oil supply or poor atomization of the injector. Should first check the injector, and then check the injection pump.
⑤ If the idle speed stabilizer is not properly adjusted, it should be rechecked on the test bench.