Idle quality is the test of a good calibration. An engine that starts quickly, settles to a steady RPM, and responds cleanly to electrical or mechanical loads feels finished. Haltech idle control strategies work with either an electronic throttle or a dedicated idle air control valve. The aim is stable airflow at idle and intelligent corrections when conditions change.

Start with the hardware. Drive-by-wire engines manage idle by commanding throttle angle. Cable-throttle engines need a bypass path. That is usually a stepper motor or a PWM solenoid feeding a neat hose to the plenum. The valve must be sized so it can deliver enough air on a cold morning with a big cam but still allow fine control when hot. Vacuum leaks defeat any strategy, so gasket faces and hoses must be tight.

Base mechanical setup comes next. Set a realistic base throttle stop so the engine will idle warm even if the valve is unplugged. Establish ignition timing that the engine likes at idle speed. With that foundation, the ECU can make small airflow and timing trims rather than fighting a poorly set throttle plate.

Targets are mapped against coolant temperature and, where useful, against gear or vehicle speed. Cold engines need more air and more timing to stay lit. As temperature rises, targets drop smoothly to a stable hot idle. Air conditioning, power steering, and fan load add torque demand at idle. Inputs for those loads allow the ECU to anticipate and feed in air before the RPM droops. For light flywheel cars or engines with big overlap, a dashpot strategy holds a little airflow as you lift the throttle, then decays gently to prevent stalls at junctions.

Ignition idle control is the fine brush. The ECU can nudge timing up and down by a few degrees to push or pull torque quickly without moving the throttle or valve. That stabilises idle against small disturbances and makes the engine feel calm rather than busy. The balance between air and timing control is tuneable so you can match the behaviour to the cam and compression.

Learning trims help day-to-day use. The ECU can adapt the base position of the valve or throttle for changes in altitude, weather, and engine wear. That prevents the slow drift that shows up as a high idle one week and a low idle the next. If battery voltage drops at night with lights and fans on, the ECU adjusts injector deadtime and idle airflow together so fuelling stays consistent.

Diagnostics are built into logs. You can see target RPM, actual RPM, idle duty or throttle angle, ignition correction, battery voltage, and load inputs. If the engine stalls when the fan comes on, you can confirm whether the ECU saw the load and how it responded. If hot restarts hang at a high idle, check whether coolant temperature is reading correctly and whether heat-soak is shifting IAT and fuelling.

A well-set idle control strategy turns a modified engine into something you can drive every day. Cold starts are quick, traffic manners are civil, and the car feels composed when accessories cycle. It is a small part of a tune that makes a big difference to how a build feels.