What causes unstable idle speed in the Haval H5?
3 Answers
There are several reasons for unstable idle speed in a car: 1. Intake manifold leakage: Air, gasoline vapor, or combustion exhaust that should not enter the intake manifold leaks into it, causing the air-fuel mixture to become too rich or too lean, resulting in abnormal engine combustion; 2. Excessive carbon buildup: Excessive carbon deposits and dirt on the throttle body and intake passages change the cross-sectional area of the air passage, making it impossible for the control unit to precisely control the idle air intake, leading to an overly rich or lean mixture and abnormal combustion; 3. Component failure: Faulty components cause inaccurate idle air control; incorrect signals received by the control unit result in wrong commands, leading to improper idle air intake control and abnormal engine combustion, which are indirect causes of unstable idle speed.
Last time, my friend's Haval H5 also had fluctuating idle speeds, and after a lot of troubleshooting, we found that the main issues were in three areas. Air intake system leaks are the most common, especially when the rubber gasket around the intake pipe has aged or the turbocharger pipe is loose, causing the engine to suck in excess air and shake. Another typical problem is excessive carbon buildup on the throttle body, making the flap stick and open/close unevenly. Additionally, a faulty oxygen sensor can cause the engine control unit to miscalculate the fuel injection, particularly during cold starts when the RPM needle dances. These faults can all lead to unstable idle speeds. It's recommended to first use a diagnostic tool to read the fault codes, focusing on these three areas.
My neighbor's H5 back home also experienced idle shaking, and I've summarized a few practical tips: First, check the fuel quality. Using poor-quality diesel with excessive water and impurities can lead to poor nozzle atomization, which is the most common cause of shaking. Second, inspect the spark plugs and ignition coils. Eroded metal pins or cracked coils can cause cylinder misfires and shaking. Third, don't overlook the engine mounts. If the rubber cushions are collapsed, vibrations will directly transfer to the steering wheel. Fourth, check for carbon buildup. If the EGR valve is completely clogged, exhaust gas recirculation will be disrupted, leading to unstable idle. Remember, for diesel vehicles, also inspect the high-pressure fuel pump pressure. If the pressure fluctuation exceeds 15%, professional repair is needed.
