Data Senders

The following data senders are used in addition to the oxygen sensor to provide the microprocessor with engine operating data.



4-151 Engine
The system on these engines uses three vacuum operated electric switches, two engine coolant operated electric switches (dual function) and one air temperature operated electric switch to detect and send engine operating data to the MCU. These senders detect cold engine start up and operation, wide open throttle when engine is cold or warm, idle (closed throttle) and partial and deep throttle.
The adaptive vacuum switch is closed during engine idle and partial throttle engine operation (adaptive mode of operation).



On 1983 and 1984 models, the switch opens at 10 inches Hg regardless of the transmission used.



In the adaptive mode, the mixture control solenoid is regulated to produce predetermined air/fuel ratios. During acceleration from idle speed to partial throttle and deceleration from partial throttle to idle speed, the oxygen sensor cannot react quick enough to the changes in the air/fuel mixture. As a result, high HC and CO emissions would be emitted momentarily unless the system switched the predetermined programmed air/fuel mixture ratios.






On 1983 and 1984 models both of the above functions are preformed by a single 4 inch Hg switch.





On 1983 and 1984 models, the open loop coolant temperature switch is open during engine warmup below 100 degrees F.






This results in the MCU not accepting the oxygen sensor voltage output and predetermined air/fuel mixture is maintained (open loop mode of operation).




The open loop thermal electric switch (TES) is attached to the inside of the air cleaner to provide either a ground circuit for the microprocessor to indicate the necessity for a cold weather engine start-up (when air temperature is below 55° F) or an open circuit to indicate normal engine start-up (when air temperature is above 65° F).
The mixture control solenoid is de-energized until a voltage equivalent to a predetermined RPM is received by the MCU and the system remains in the open loop mode of operation resulting in a rich air/fuel mixture for engine starting purposes. This RPM voltage received by the MCU is referred to as ``engine RPM (tach) voltage''. In order for this system to operate properly, all associated components and related systems must be intact and operational. This includes the EGR valve and related components, correct ignition advance vacuum hose routing, etc.