Car starts then immediately dies
An engine that fires up and runs for a second or two before stalling is almost always losing fuel, air, or idle control right after the richer starting mixture cuts out, rather than having an ignition problem - ignition faults usually prevent starting altogether rather than letting it run briefly first. Where exactly it dies (instantly vs after a couple of seconds) narrows down which system.
Urgency
Visit a workshop soon
Possible causes, most likely first
- Faulty or dirty idle air control valve
Once the starting enrichment cuts out, the engine needs the idle air control valve to hold a stable idle airflow; a stuck or dirty valve can't maintain it and the engine stalls as revs sag below the point where it can sustain itself. Watch the idle RPM right after starting for a sharp drop rather than settling smoothly. - Weak fuel pump losing pressure right after start
A pump that can build enough pressure for the initial fire but can't sustain it stalls the engine within a second or two as the fuel rail pressure drops. Check fuel pressure immediately after a stall attempt with a gauge, watching for a fast decay. - Vacuum leak in the intake
A cracked hose or loose intake connection lets in unmetered air that the ECU can't fully compensate for once it switches out of the rich starting map, causing a stall. Spray a small amount of water or use a smoke test around intake joints while listening for an idle change. - Intermittent crank or camshaft position sensor signal
A sensor with a marginal signal can support the initial crank-triggered fire but lose the signal the ECU needs to keep timing fuel and spark once the car tries to idle on its own. Check for a stored intermittent code for either sensor. - Clogged fuel filter restricting flow
A filter that's nearly blocked may pass enough fuel for the initial start pulse but can't sustain the flow needed even at idle, causing a quick stall. Check fuel filter age against the service schedule. - Faulty throttle position sensor
A sensor reporting an incorrect throttle position confuses the ECU's idle fuel and air calculation right as it transitions from start mode to idle mode, causing a stall. Check live throttle position data at idle on a scan tool for an unstable or incorrect value.
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What you can check yourself
- Note exactly how long it runs before dying: instantly, or after one to three seconds.
- Try starting with a very light touch on the accelerator to see if that keeps it running.
- Check for a stored or pending fault code even if the warning light isn't on yet.
- Listen for any hissing sound around the intake/engine bay that would suggest a vacuum leak.