Pre-ignition Pre-ignition Pre-ignition (or preignition) in a spark-ignition engine is a technically different phenomenon from engine knocking, and describes the event wherein the air/fuel mixture in the cylinder ignites before the spark plug fires. Pre-ignition is initiated by an ignition source other than the spark, such as hot spots in the combustion chamber, a spark plug that runs too hot for the application, or carbonaceous deposits in the combustion chamber heated to incandescence by previous engine combustion events. The phenomenon is also referred to as 'after-run', or 'run-on' or sometimes dieseling, when it causes the engine to carry on running after
Ignition interlock device Ignition interlock device An ignition interlock device or breath alcohol ignition interlock device (IID or BAIID) is a breathalyzer for an individual's vehicle. It requires the driver to blow into a mouthpiece on the device before starting the vehicle. If the resultant breath-alcohol concentration analyzed result is greater than the programmed blood alcohol concentration (which varies between countries), the device prevents the engine from being started. The interlock device is located inside the vehicle, near the driver’s seat, and is directly connected to the engine’s ignition system. An ignition interlock interrupts the signal from the ignition to the starter until