- I -

Idler Gear

1. A gear connecting two other gears in a manner so that they will turn in the same direction. 2. A gear that transmits movement between the drive and the driven gears, but does not affect the speed relationship of those gears.

Idler Pulley

A pulley that is used to adjust the belt in a belt-driven system.

IDM

Ignition diagnostic monitor.

IEC

International Electrotechnical Commission.

IES

Idle enrichment system.

IESR

Ignition electronic spark retard.

If You Can't Find 'em, Grind 'em

An admonition to a driver who misses a shift.

IFI

An acronym for Inline Fuel Injection.

IFS

Inertia fuel shut-off.

Ignition

The firing of a spark plug to ignite the air/fuel mixture in the combustion.

Ignition

When a spark plug fires in an engine to ignite the air and fuel mixture during the combustion process. A spark plug is the final component in a vehicle's ignition system.

Ignition Advance

The moving forward, in time, of the ignition spark relative to the piston position.

Ignition Box

A product that will increase the voltage to a vehicle's coil, which in turn provides the engine with increased spark energy. This helps produce a more complete burn of the air and fuel mixture, for both more power and better fuel economy. Many ignition boxes also provide multiple sparks, instead of firing just once per cycle, which also is designed to create a more complete burn. Additional benefits of an ignition box include quicker throttle response, smoother idling and starting, and reduced emissions.

Ignition Coil

A transformer containing a primary and secondary winding that acts to boost the battery voltage of 12 volts to as much as 30,000 volts to fire the spark plugs.

Ignition Distributor

A term used for distributor.

Ignition Map

A chart showing the precise advance and retard of the ignition on an electronic control-equipped engine.

Ignition Points

A term used for points.

Ignition Reference Signal

Signal used by the ECM to determine engine RPM and crankshaft position.

Ignition Reserve

The difference between the minimum available and maximum required voltage for proper operation.

Ignition Resistor

A resistance element in series with the primary circuit to reduce the voltage supplied to the coil during engine operation.