What are the reasons for unstable idle speed in Jetour X90?
2 Answers
Jetour X90 unstable idle speed reasons: Severe engine carbon deposits: When there is excessive carbon buildup inside the engine, the gasoline sprayed by the cold-start injector will be largely absorbed by the carbon deposits, resulting in an excessively lean mixture during cold starts and making it difficult to start. Under these conditions, the engine will only start easily after the carbon deposits have absorbed enough gasoline to become saturated. After starting, the gasoline adsorbed on the carbon deposits will be drawn into the cylinders by the engine's vacuum suction and burned, making the mixture too rich. The combustible mixture in the engine alternates between being too lean and too rich, causing idle speed fluctuations after a cold start. Excessive carbon deposits and dirt in the throttle body and intake passages: Excessive carbon buildup and dirt in the throttle body and surrounding intake passages change the cross-sectional area of the air passages, making it impossible for the control unit to precisely regulate the idle air intake. This results in an excessively rich or lean mixture, leading to abnormal combustion. Weak spark due to faulty spark plugs: Spark plugs can also accumulate carbon deposits, which can be cleaned to restore their performance. However, some spark plugs may be nearing the end of their service life, leading to reduced performance. Weak sparks from spark plugs in individual cylinders can affect the car's performance. Faulty spark plugs can cause the engine to "misfire," but minor faults in individual spark plugs may only cause unstable idle speed. Fuel pressure issues: If the fuel pressure is too low, the fuel sprayed by the injectors will not atomize properly or may spray in a stream rather than a mist. In severe cases, only droplets may be sprayed, reducing the fuel supply and making the mixture too lean. If the fuel pressure is too high, the actual fuel injection volume increases, making the mixture too rich. Various component failures: Leaks in the intake manifold or various valves, fuel pressure issues (too low), ignition system faults, etc., can also cause unstable engine idle speed.
I've been running this auto repair shop for twenty years, and unstable idling in the Jetour X90 is quite a common issue. Most of the time, it's due to excessive carbon buildup in the throttle body. Poor-quality gasoline leads to carbon deposits that affect the air intake, making the engine 'gasp' and causing the RPM to fluctuate. Another reason could be an aging ignition system—like worn-out spark plugs causing misfires, which leads to severe shaking at idle. A clogged air filter can also be the culprit, as dirty air intake results in incomplete combustion. Sensor malfunctions are another headache; if the mass airflow sensor or throttle position sensor isn't responsive, the electronic control unit will incorrectly adjust the fuel supply, causing RPM swings. Don’t overlook vacuum hose leaks either—cracked hoses leaking air can worsen unstable idling. My advice is to pop the hood and check the air filter and spark plugs first. If it's just carbon buildup, you can clean it yourself. But for sensor-related issues, it’s best to visit a professional shop to scan for trouble codes with a diagnostic tool to avoid major problems that could compromise driving safety. Regular cleaning and maintenance can prevent this, and choosing good-quality fuel is also crucial.
