See Figure 1
The 4A-GE engines are equipped with the Electronic Spark Advance (ESA) system. The Electronic Control Unit (ECU) is programmed with data for optimum ignition timing under any and all operating conditions. Using the data provided by the sensors which monitor the various engine functions (rpm, intake air volume, engine temperature ect.) the ECU triggers the spark at precisely the right instant.
The Integrated Ignition Assembly (IIA) is a typical electronic ignition system. There are two types of this system used on Corollas. On the 4A-F engines, the major components consist of an integral ignition coil, signal generator (pick-up), igniter, vacuum and governor weight advance system and a rotor and distributor cap distribution system.
On the 4A-FE and 7A-FE engines equipped with the IIA system the major components consist of an integral ignition coil, igniter, pick-up coils, condenser (on some models), IIA wire (on some models), rotor and distributor cap.
Service on these electronic ignition systems consists of inspection of the distributor cap, rotor and the ignition wires, replacing them as necessary. In addition, the air gap between the signal rotor and the projection on the pickup coil should be checked periodically.