Engine Keeps Running After Switching Off
An engine that coughs or keeps running for a moment after the ignition is off is usually dieseling on older carburettor engines; on modern cars, a faulty ignition switch or relay is more likely. A fan or pump running after switch-off is normal.
Normal risk
Usually not dangerous, but have it checked. A diesel that runs away and revs uncontrollably is an emergency.
Short answer · Why does my engine keep running after I turn it off?
On older petrol engines, hot spots and carbon deposits can ignite fuel after the ignition is off, which makes the engine shudder and run briefly. Modern fuel-injected engines cut fuel instantly, so run-on usually points to an electrical fault keeping the system powered. Do not confuse it with cooling fans or pumps that keep running by design.
Safe checks you can do
- Check what is still runningFan or pump noise is normal; the engine itself turning is not.
- Check the ignition lightsIf dashboard lights stay on, the switch may be faulty.
- Note engine temperatureOverheating makes run-on more likely on old engines.
Questions that narrow it down
- Is it an older carburettor engine?Dieseling is typical.
- Do dashboard lights stay on?Ignition switch or relay fault.
- Is it a diesel revving uncontrollably?Possible runaway; emergency.
Possible causes
Listed without ranking. Use the questions above to see which ones fit your car.
- Carbon deposits and hot spotsOlder petrol engines.
- High idle or overheatingEncourages run-on.
- Faulty ignition switchPower stays on.
- Stuck relaySystem remains powered.
Questions about Engine Keeps Running After Switching Off
What is a diesel runaway?
A diesel burning its own oil and revving out of control; stall it in a high gear with the brakes on if safe, and get away.
Is a fan running after switch-off normal?
Yes, many cars cool the engine this way.