Engine Temporary Running after Switch Off

what would be the cause for engine to temporary keep running for few seconds after been switched off?

Does the ECU features an ignition input (i.e. a Run/Stop switch), or are you just turning the power to the ECU off?

For race cars where we have a battery disconnect switch, we need to make sure the ECU knows to stop, because the alternator output will continue to provide power even with the battery disconnected.

Lastly, an engine can "diesel" without a spark if there is enough heat in the spark plug or deposits in the cylinder to keep igniting the mixture. Diesel engines are stopped by turning off the fuel injection.

A turbo timer installed in the car would do that...

Honestly, it's a pretty vague question. It depends on how the wiring was done, like when you turn the key off, what circuit does it cut off? I've seen bad ground design that kept the ECU relay engaged for a while after the key was turned off, therefore keeping the ignition relay that was controlled by the ECU engaged as well. Does everything in the cluster stay on as well, or only the engine keeps running?

Did you resolve this issue?