An engine that stalls is losing one of the things it needs to keep running: air, fuel, spark or the crankshaft signal that times them. When it stalls narrows the cause down: stalling at idle or when coming to a stop usually points to idle control or a torque converter clutch that will not release, while stalling at speed points to fuel delivery, a failing crankshaft position sensor or an electrical problem.
When it stalls and why
| When | Common causes |
|---|---|
| At idle or with the AC on | Dirty throttle body or idle air control valve, vacuum leak |
| When coming to a stop (automatic) | Torque converter clutch stuck on (P0742), idle control |
| While driving, often when hot | Failing crankshaft position sensor (P0335), fuel pump |
| Under load or uphill | Clogged fuel filter, weak fuel pump, low fuel pressure |
| Right after starting | Anti-theft system not recognizing the key, fuel pressure, idle control |
| With dimming lights or a battery light | Charging system; see battery light on |
How to diagnose stalling
- Read codes, including pending codes; see how to use an OBD2 scanner.
- Note exactly when it stalls: cold or hot, at idle, when stopping or at speed.
- Watch engine speed on a scan tool or the tachometer: a tachometer that drops to zero just before the stall points to the crank sensor.
- Check fuel pressure, and listen for the fuel pump priming with the key on.
- Clean the throttle body and check for vacuum leaks if it stalls at idle.
Stalling after a battery change or throttle cleaning
Many engines store learned idle settings. After the battery is disconnected or the throttle body is cleaned, idle can be unstable and the engine may stall at stops until it relearns. Most vehicles relearn on their own after a few drives, while others need a specific idle relearn procedure or a scan tool; see throttle body for the details.
Is it safe to drive?
Stalling in traffic is dangerous: power steering and brake assist are reduced with the engine off. If the engine stalls while driving, shift to neutral, steer to safety and restart once stopped. Repair the cause before relying on the vehicle; see also car won’t start and engine sputtering.
Manual transmission stalling
On a manual, stalling when pulling away can simply be clutch technique, but a clutch that engages abruptly or a dragging clutch also causes it; see signs of a bad clutch. If an engine keeps stalling because it has low compression or internal damage, compare replacements on our engines page.
Trouble codes: P0369 Cam Sensor B Intermittent · P2176 Idle Position Not Learned · P0231 Fuel Pump Secondary Circuit Low · P0320 Engine Speed Input Circuit · all OBD2 codes.
Shipping is a flat $80.00 per order to US addresses, with 15-day free returns. Questions? Ask a parts specialist.