1991-1994 Mercury Capris have a multitude of modules, controls, sensors, solenoids, actuators, and relays to manage and control the operation of the 1.6 engine and meet emission standards. Each component has an effect on performance, fuel economy and exhaust emissions. The list below attempts to identify, explain the function, and the location of the various Capri engine management controls.

A/C RELAY (ACR)- Is controlled by the PCM (powertrain control module) with an output signal. The PCM will cut off the A/C relay during wide open throttle conditions.

location: Behind the LH strut assembly

BAROMETRIC PRESSURE SENSOR (BARO)- Detects changes in atmospheric pressure. This info is transferred to the PCM/ PCM adjusts air/fuel ratio, A/C cut off, idle speed & purge control to compensate for the changing pressure.
location: Passenger side cowl

BOOST PRESSURE SWITCH (BPS)- On Turbo engines sends a signal to PCM when the turbo boost pressure reaches 10.4-11.6 psi. Controls turbo overboost. location: Behind the intake manifold

BRAKE ON/OFF SWITCH (BOO)- Detects when the brake pedal is depressed & sends a signal to the PCM. Information is used to control fuel injection amount.
location: Mounted on top of brake pedal.

BYPASS AIR VALVE (BPA)- This valve consists of a thermowax material that expands or contracts depending on engine coolant temperature. When cold BPA supplies air to increase idle speed for improved cold engine performance.
location: Mounted to RH of intake manifold.

CANISTER PURGE SOLENOID (CANP)- Regulates the amount of evaporative fuel vapors transferred front the carbon canister into the intake manifold. Operates by an output signal from the PCM to open the vacuum passage between the carbon canister and the intake manifold when purging conditions are met.
location: Mounted near center of cowl panel.

CARBON CANISTER (CC)- The fuel vapors from the fuel tank are stored in the carbon canister. when the vehicle is being operated, the fuel vapors are purged from the CC into the engine by means of the purge solenoid.
location: RH corner near cowl panel.

CLUTCH PEDAL POSITION SWITCH (CPP)- Detects when the clutch pedal is depressed and signals PCM with input information.
location: Mounted at top of clutch pedal.

CYLINDER IDENTIFICATION SENSOR (CID)- Detects the number 1 cylinder when it reaches Top Dead Center (TDC) and signals the PCM to control fuel injection.
location: Attached to distributor housing (external) on non turbo, Integrated in the distributor on turbo.

ENGINE COOLANT TEMPERATURE SENSOR (ECT)- Detects the coolant temperature, and updates the PCM on the coolants changing condition with an input signal. PCM uses this data to modify timing, air/fuel ratio, idle speed, and purge flow.
location: Threaded into the underside of the intake manifold.

Fuel Injector (INJ)- Solenoid operated needle valves that control the fuel flow into the engine.
location: Mounted on the fuel rail and attached to the intake manifold.

Fuel Pressure Regulator (FPR)- Adjusts the amount of fuel pressure supplied to the fuel injectors. The FRP is controlled by a vacuum actuated diaphragm inside the FRP.
location: Mounted to the fuel rail on the LH side of the engine.

Fuel Pressure Regulator Control Solenoid (FPRC)- Monitors and adjusts the amount of vacuum applied to the FPR by an output signal from the PCM.
location: Mounted on the cowl panel next to the CANP solenoid.

Fuel Pump (FP)- Filters the solid particles and allows the fuel to be transmitted from the tank to the engine.
location: Mounted under bottom of rear seat on the top of the fuel tank.

Fuel Pump Relay (FPR)- Supplies voltage to the fuel pump when activated.
location: Mounted on the firewall forward of the console to the left of the PCM.

Idle Air Control Solenoid (IAC)- Controlled by a duty cycle emitting from the PCM. The internal solenoid opens as the signal on time increases, raising the amount of bypass air allowed into the engine.
location: Mounted on the RH side of the intake manifold.

Idle Air Control Bypass Air Valve (IAC BPA)- Allows bypass air to flow into the intake manifold during cold engine conditions. Controlled by two components, the BPA valve and the IAC solenoid.
location: Mounted on the RH side of the intake manifold.

Idle Switch (IDL)- When the throttle plate is closed, an idle condition occurs. IDL switch detects this position and notifies the PCM with an input signal so adjustments can be made to air/guel ratio and idle speed.
location: Integrated in the throttle position sensor.

Ignition Control Module (ICM)- Is an output device controlled by the PCM. The PCM sends a signal to the module. The module transfers the signal to the ignition coil where it is generayed into a high voltage spark to the spark plugs.
location: Mounted in the distributor.

Ignition Switch (IGN)- Directs voltage to the vehicle's systems according to its position. The PCM detects the IGN position by a series of inputs, and controls the vehicle's operation based on this information.
location: Mounted on the steering column.

Intake Air Temperature Sensor (IAT)- Detects the incoming airflow temperature. As the air temp increases, the resistance of the sensor increases. The resistance, sent to the PCM as an input signal is used as a temperature-to-density calculation. the PCM can then determine the air density and cold enrichment fuel flow.
location: Intergrated in the volume air flow meter.

Knock Control Module (KCM)- On Turbo emgines monitors the knock sensor and determines the severity of the vibration. If the vibration becomes excessive, the KCM notifies the PCM with an input signal.
location: Mounted forward of the RH shock tower.

Knock Sensor (KS)- On Turbo engines detects when the engine experiences excessive vibration. The vibration is transferred to the PCM as a voltage signal. The PCM regulated timing to compensate for the condition.
location: Threaded in the engine block near the the oil pressure switch.

Manual Lever Position Switch (MLP)- On automatic transmissions purpose is to notify the PCM when the vrhicle is in PARK or NEUTRAL position for starting. It also detects when the switch is in a forward or reverse gear so a voltage signal can be sent to the TCM to control the transaxle.
location: Mounted on the top portion of the automatic transaxle.

Oxygen Sensor (O2S)- Generates and supplies a signal to the PCM which reflects oxygen content in the exhaust system. The oxygen in the exhaust reflects if the exhaust gas is rich or lean. The PCM uses this info to regulate the the fuel injectors for proper air/fuel mix.
location: Threaded in the exhaust manifold

Park/Neutral Position Switch (PNP)- Detects whether the vehicle is IN GEAR or in NEUTRAL position. The switch informs the PCM of the automatic transaxle's present condition.
location: Threaded to the transaxle, on the bottom RH side.

Positive Crankcase Ventilation Valve (PCV)- Controls the amount of blow-by gas from the crankcase allowed into the intake manifold. A one-way valve, does not allow anything from the intake manifold back into the crankcase.
location: Plugged into the RH top of the valve cover.

Power Steering Pressure Switch (PSP)- When the power steering fluid pressure exceeds the preset limit, the PSP switch sends an input signal to the PCM which adjusts idle speed.
location: Threaded into the power steering pump.

Powertrain Control Module (PCM)- Is the microprocessor (brain) of the vehicle. PCM receives and transmits to and from relays, sensors, actuators, switches and other electronic components. From the information gained the PCM controls fuel economy, drivability, and optimizes emissions. It also performs self-diagnosis and detects failures within the electronic engine control system.
location: Mounted under instrument panel behind and below the radio.

Rollover/Vent Valve (ROVV)- Serves a dual purpose. When fuel is in the tank, pressure increases. The ROVV releases the extra pressure into the atmosphere. If a rollover situation occurs, the ROVV closes and will not permit fuel or vapors to escape the fuel tank.
location: Highest point of the fuel tank.

Catalyic Converter (CC)- Reduces air pollutants HC, CO, NOx. The CC removes these pollutants from the exhaust gases by means of a chemical reaction.
location: Between the exhaust header/down pipe and the muffler.

Throttle Body (TB)- Controls the amount of air that flows into the engine through a single butterfly valve determined by the accelerator pedal position. TB is cast with an air bypass channel, and houses several emission related components for the PCM.
location: Mounted on the top of the intake manifold.

Throttle Position Sensor (TP)- A two position switch that detects the throttle plate position (Idle & Wide Open) and supplies the PCM with an input signal indicating throttle position.
location: Mounted on the throttle body.

Two Way Check Valve (TWCV)- Controls pressure between the fuel tank and the carbon canister. Allows pressure to go either way depending on the pressure applied to the check valve.
location: Mounted to the body above the fuel tank.

Volume Air Flow Meter (VAF)- Measures air flowing into the engine and provides an input to the PCM which then translates the vane position into the volume of air flowing into the engine.
location: Mounted on the air cleaner tank assembly.

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