General System Description

PURPOSE/OPERATION
The Sequential Multiport Fuel Injection (SFI) system is composed of 3 basic sub-systems: Fuel, Air Induction and Electronic Control Systems.

Fuel System
Fuel is supplied under constant pressure to the Sequential, injectors by an electric fuel pump. The injectors inject a metered quantity of fuel into the intake manifold in accordance with signals from the ECM (ECM).

Air Induction System
The air induction system provides sufficient air for engine operation.

Electronic Control System
This engine is equipped with a TOYOTA Computer Controlled System (TCCS) which centrally controls the SFI, Electronic Spark Advance (ESA), Idle Air Control (IAC), diagnosis systems etc. by means of ECM (formerly SFI computer) employing a microcomputer.

The ECM controls the following functions:

1. Sequential Multiport Fuel Injection (SFI)
The ECM receives signals from various sensors indicating changing engine operating conditions such as:
- Intake air volume
- Intake air temperature (IAT)
- Engine coolant temperature (ECT)
- Engine speed (RPM)
- Acceleration/deceleration
- Exhaust oxygen content etc.

The signals are utilized by the ECM to determine the injection duration necessary for an optimum air-fuel ratio.

2. Electronic Spark Advance (ESA)
The ECM is programmed with data for optimum ignition timing under all operating conditions.
Using data provided by sensors which monitor various engine functions (RPM, ECT, etc.), the ECM triggers the spark at precisely the right instant.

3. Idle Air Control (IAC)
The ECM is programmed with target idling speed values to respond to different engine conditions (ECT, air conditioning (A/C) ON/OFF, etc.). Sensors transmit signals to the ECM which control the flow of air through the throttle valve bypass and adjust idle speed to the target value.

4. Diagnosis Function
The ECM detects any malfunctions and abnormalities in the sensor network and lights a malfunction indicator lamp (MIL) in the combination meter. At the same time when trouble is identified an appropriate diagnostic trouble code (DTC) is recorded by the ECM. The DTC can be read by the number of blinks of the MIL when terminals TE1 and E1 of the data link connector 1 (DLC1) are connected. The DTC are referred to in a later page.

5. Self-Correction Function
If any sensor malfunctions, an average value recorded in the back-up circuit is substituted to make driving possible. If danger is predicted, the engine is stopped and the MIL will light up.

6. Fail-Safe Function
In the event of the sensor malfunctioning, a back-up circuit will take over to provide minimal driveability, and the MIL will illuminate.