Car stalls while driving

Symptoms

• Engine suddenly cuts out while driving, sometimes restarting
• Warning lights may flash before or during the stall
• Power steering and brakes become harder to use once the engine is off
• May happen more when the tank is low or fuel is hot

Likely causes

• CommonFailing fuel pumpA weakening pump can't maintain pressure, especially when hot or the tank is low, causing the engine to starve.
• CommonFailing crankshaft or camshaft position sensorThese sensors tell the computer when to fire spark and injectors; failure can cut the engine instantly.
• PossibleClogged fuel filterSevere restriction can starve the engine under load or at speed.
• PossibleIgnition switch or wiring faultAn intermittent electrical fault can momentarily cut power to the engine.
• Less commonAlternator or battery failure cutting engine electronicsA sudden total charging system failure can starve the engine's electronics.

What to do

1. If it stalls, safely pull off the road as soon as possible, since you'll lose power steering and braking assist.
2. Note exactly what was happening when it stalled: speed, temperature, fuel level, and any warning lights.
3. Get the check engine light scanned for stored codes, especially position sensor or fuel-related ones.
4. Avoid driving on a very low fuel level until diagnosed, since some fuel pump issues worsen with less fuel.
5. Have the fuel pump, fuel pressure, and crank/cam sensors tested by a shop.
6. Do not ignore repeat stalling; have it diagnosed before it happens somewhere unsafe, like a highway or intersection.

Tools and parts

• OBD-II code reader

When to call a pro

This needs a shop diagnosis promptly; intermittent stalling caused by a sensor or fuel pump can strand you or cause an accident if it happens at highway speed.

Safety