Did you see any MAP related trouble codes with the bad EEC?
Was thinking about the "high-altitude EEC", but my memory lit up, it's an emissions compliance statement.
Carbureted Broncos significant changes range from a different PCV Valve, Smog Pump BELT & Pulley, Timing Change (figuring it's retarded about 3 to 4 degrees, IDLE IS ADJUSTED, different alternator & different modulator valve if C6 equipped; new choke rod lever, different fuel/air mixture by changing metering jet.
EEC IV Broncos Overview;
"...Determining how much fuel to deliver is accomplished in two ways, Speed Density (SD) control or Mass Air Flow (MAF) control. The mass airflow sensor measures the *MASS* of the air going into the engine. By measuring the *MASS* of the air, this helps to compensates for air density changes that occur with altitude and weather changes. The air temperature sensor, the engine temperature sensor, and the Oxygen Sensors (O2 or HEGO) are also used to help determine fuel and timing requirements. Both the MAF and SD systems use barometric compensation with the exception of the ‘94-’95 Mustangs which incorporate that function into the MAF. The SD system uses a Manifold Absolute Pressure sensor (MAP), which measures the absolute pressure (vacuum) in the intake manifold. When the ignition is first turned on, the EEC takes a quick reading of the MAP and stores that value as atmospheric barometric pressure for calculations during running..." in EEC IV Inner Workings by T Moss @ EEC IV Inner Workings
"...The Manifold Absolute Pressure (MAP) sensor operates as a piezoelectric (pressure-sensing) disc. However, rather than generating a voltage, its output is a frequency change. The sensor changes frequency relative to intake manifold vacuum. The sensor frequency increases as vacuum increases. The MAP sensor allows the PCM to determine what the engine load is. Its signal affects air/fuel ratio, ignition timing, EGR flow and altitude compensation..." by Ryan M
The powertrain control module monitors this signal to determine altitude. The PCM then adjusts the E4OD shift schedule and EPC pressure for altitude. On diesel engines, the MAP sensor measures boost pressure. The PCM monitors this signal and adjusts EPC pressure. Symptoms: Firm shift feel, late shifts at altitude.
Mass Air Flow Sensor;
by Ryan M.
Will look through my old notes tomorrow for further details.