Carbureted Engines

On 6149 model carburetors, the A/C cut-OFF switch is controlled by the EEC computer and by the throttle position sensor (TPS). Also, altitude compensation is controlled by the EEC computer by means of an input from the barometric pressure sensor.

Input & Output System Operation

1. Profile ignition pickup (PIP) is located in the distributor and supplies ECA signals for the tachometer and crankshaft position. The output signals affected are as follows:
a. Spark timing.
b. Air/fuel ratio.
c. DC motor idle speed control (ISC).
d. Upshift light.
2. The throttle position sensor (TPS), transmits signals to the ECA for throttle position (opened or closed). The output signals affected are as follows:
a. Selects operating modes (closed, part throttle, wide open throttle).
b. Fuel enrichment at wide open throttle.
c. Wide open throttle, A/C cut-OFF.
d. Stops canister purge during wide open throttle, deceleration and at idle.
e. DC motor idle speed control (ISC).
f. Cold start kickdown.
g. By-passes thermactor air during wide open throttle and deceleration.
3. The engine coolant temperature sensor (ECT) provides an engine coolant temperature signal. The output signals affected are as follows:
a. Air/fuel ratio.
b. Idle speed.
c. Upshift light.
d. Canister purge control and thermactor air.
4. Neutral start switch signal indicates whether or not transmission is in gear. The output signals affected are the idle speed and self-test controls.
5. Exhaust gas oxygen sensor (EGO), which is threaded into the exhaust manifold measures the oxygen content in the exhaust gasses. The output signal affected is the feedback control solenoid (air/fuel ratio).
6. Ignition key POWER. The input component function is the position of the ignition switch either in Crank or Run positions. The output signals affected are as follows:
a. Self-test (key-OFF or engine running).
b. Pre-position and anti-diesel.
7. A/C compressor clutch. With the A/C ON, then ECA will receive a signal whenever the clutch is engaged. The output signal affected is the DC motor idle speed control (ISC).
8. MAP sensor. Provides signals related to engine load and barometric pressure (altitude). The output signals affected are as follows:
a. DC motor idle speed control (ISC).
b. Air/fuel ratio.
c. Thermactor air control.
d. Spark timing.
e. Canister purge valve (CANP) and upshift light.
9. Idle tracking switch (ITS) is located on the end of the idle speed control motor. When the switch is opened by the throttle lever, the ECA receives a closed throttle signal. The output signal affected is the DC motor idle speed control (ISC).