What causes the unstable idle speed of the Zhijun, fluctuating between high and low?
2 Answers
The reasons for the unstable idle speed of the Zhijun, fluctuating between high and low, are as follows: Severe engine carbon buildup: The most common cause of car shaking is a dirty throttle body or excessive carbon buildup in the fuel injectors. When there is too much carbon buildup inside the engine, the gasoline sprayed by the cold start injector is largely absorbed by the carbon deposits, resulting in an overly lean air-fuel mixture during cold starts, making it difficult to start. Ignition system issues: Check the working condition of the spark plugs, high-voltage wires, and ignition coils. Poor performance of the ignition system or inadequate spark plug firing can also lead to such faults. The solution is to check if the spark plugs have excessive carbon buildup and replace them if necessary. Unstable fuel pressure: If you have already cleaned the engine carbon deposits, cleaned the throttle body, replaced the gaskets and spark plugs, but still notice the car shaking at idle, it is recommended to check the fuel supply pressure and the intake pressure sensor for proper functioning. Abnormal fuel pump supply pressure or incorrect readings and poor performance of the intake pressure sensor can cause the car to shake. The solution is to check the fuel pressure and replace the components if necessary.
I had an old car that also experienced unstable idling with fluctuating RPMs, mostly caused by a few common issues. First, it could be a dirty throttle body with too much carbon buildup affecting air intake control, or the idle control valve being stuck and failing to regulate the RPM properly. If the fuel injectors are clogged, causing uneven fuel supply, the engine will run roughly. Worn-out spark plugs failing to ignite or leaking high-voltage wires can also cause trouble. A faulty mass airflow sensor providing incorrect air volume readings will prevent the ECU from controlling precisely. Vacuum leaks disrupting the negative pressure environment can make the idle erratic. I’ve also found that loose battery terminals or an unstable alternator delivering weak current can be culprits. If you neglect regular maintenance, these problems tend to surface. I recommend checking the air filter cleanliness and fuel system condition weekly. If idle instability occurs, do a simple inspection yourself before taking it to a mechanic to save some money.
