What Causes the Engine to Stall When Pressing the Clutch?
4 Answers
The engine itself has stalled while driving. Here is the relevant information: 1. Cause: The engine is still running because the clutch is engaged, but when the clutch is pressed, it stalls immediately. There are many possible causes for this issue, and it is safest to have it inspected at a 4S shop. Otherwise, it poses a significant risk to driving safety. 2. Fault: If the car can be restarted immediately, there are two possible faults. One is that the idle control valve intermittently gets stuck, and the other is that your EGR valve occasionally gets stuck. Both of these issues require inspection at a 4S shop to be properly diagnosed.
Last time I drove to the outskirts, my car stalled when I pressed the clutch at a red light, making me sweat with anxiety. Later, I found out through research that it was mostly due to a dirty throttle body, where carbon deposits blocked the air intake, causing unstable engine idling. The mechanic mentioned that most new cars nowadays have an idle control valve, and if this part gets stuck by sludge, it can cause the RPM to suddenly drop. My old car also has another annoying issue – a faulty clutch switch. This component is supposed to signal the computer to increase fuel injection when the clutch is pressed, but it failed, cutting off the engine's fuel supply directly. It's recommended to clean the throttle body first and then check these two components, rather than foolishly replacing the entire clutch assembly like I did.
I've repaired hundreds of cars that stall when depressing the clutch, and nine times out of ten it's an idle speed issue. The most common culprit is aged engine mounts - when the rubber cracks, the engine shakes violently like sifting flour the moment you press the clutch, instantly killing the engine. Another often overlooked factor is spark plugs; excessive electrode gap or heavy carbon buildup causes ignition efficiency to plummet at low RPMs. My standard procedure is having owners first plug in an OBD scanner to read fault codes. If the idle control valve shows abnormal voltage fluctuations, I disassemble and clean it while checking the clutch pedal's travel switch for poor contact. For older German cars, pay extra attention to vacuum hose leaks as air leakage leads to over-lean mixture and stalling.
As a driving instructor, I've noticed that 80% of stalling when students depress the clutch is due to operational errors. However, there was indeed a training car that stalled twice in two clutch depressions. Upon inspection, we found the fuel injector O-ring had aged and was leaking, causing insufficient fuel supply at idle. This issue doesn't manifest during normal driving, only when the clutch is depressed and the engine load suddenly changes, cutting off fuel. Additionally, loose battery terminals can cause similar symptoms, with unstable current transmission affecting ECU control. Now when encountering such vehicles during lessons, I instruct students to first press the accelerator deeply to maintain 2000 RPM. If it still stalls, operational issues can be basically ruled out, and we need to check the electrical and fuel systems.
