What Causes a Car to Stall When Releasing the Throttle Without Idling?
2 Answers
If a car stalls after releasing the throttle without idling, it may be due to damage to components such as the throttle body or idle control valve. When the engine stalls at idle, the idle speed should be adjusted based on the actual situation. If the issue disappears after adjustment, it indicates improper idle screw adjustment. Clogging of the idle jet and idle fuel passage: During idling, the idle motor on the throttle body controls the amount of air entering the engine. If the motor is damaged, it can lead to unstable idling or stalling. It is important to note that prolonged use of the throttle body can easily lead to carbon buildup. Therefore, it is recommended that owners regularly clean and maintain the throttle body to remove carbon deposits. Intake pipe leakage: If there is a leak in the intake pipe, the air flow sensor cannot accurately measure the actual intake air volume, causing the electronic control unit (ECU) to inaccurately control the air intake. This results in unstable idling and stalling. Additionally, fuel injector leakage or clogging, as well as circuit faults, can affect the quantity and quality of fuel injection, preventing it from following the ECU's instructions. This leads to an overly rich or lean air-fuel mixture, causing poor performance in individual cylinders and unstable idling.
I've been driving for over a decade, and this stalling-when-coasting issue isn't my first encounter. The most common culprit is excessive carbon buildup in the throttle body, preventing the valve from sealing properly and starving the engine of air at idle. A faulty or stuck idle air control valve (IACV) that can't regulate airflow is another frequent offender. Fuel delivery problems are equally critical—an erratic fuel pump or clogged injectors will disrupt idle fuel supply. The ignition system should also be scrutinized; worn spark plugs or leaking ignition coils can cause combustion failures. For older vehicles, inspect vacuum lines for leaks. Last time I faced this, a ¥200 throttle body and IACV cleaning did the trick—hold off on major repairs until diagnosing these basics.
