Jeep Engines - Oljeep

222 MOPAR PERFORMANCE PARTSINTAKE MANIFOLDThe 4.0L engine standard production intake manifold ismade of cast aluminum and uses eleven bolts to mount tothe cylinder head (Figure 4-48). This mounting styleimproves sealing and reduces the chance of leaks.Removal and InstallationThe engine intake manifold and exhaust manifolds must beremoved and installed together. The manifolds use acommon gasket at the cylinder head. Refer to ExhaustMuni&dolds, ‘Exhaust System’ section of this chapter formore information.MULTI-POINT FUEL INJECTION (MPI)The 4.0L engine uses a sequential Multi-Port Fuel lnjection(MPI) system. Fuel is injected into the intake manifoldbefore the intake valve in precise metered amounts throughelectrically operated injectors. The injectors are fired in aspecific sequence by the Powertrain Control Module (PCM).The PCM constantly adjusts the amount of fuel injected tomeet changing operating conditions by controlling injectorpulse width (the length of time the injector is energized). ThePCM also adjusts ignition timing by controlling the ignitioncoil operation through the Ignition Control Module (ICM).The PCM determines air-fuel mixture and ignition timingbased on inputs it receives from various sensors that monitorengine operating conditions.The PCM receives inputs from sensors that react to exhaustgas oxygen content, coolant temperature, manifold absolutepressure, engine speed (crankshaft position), throttleposition, battery voltage, intake manifold air temperature,engine knock and transmission gear selection. These inputsrepresent the engine’s instantaneous operating conditions.Air-fuel mixture and ignition timing calibrations forvarious driving and atmospheric conditions are preprogrammedinto the PCM. The PCM monitors andanalyzes its various inputs, computes engine fuel andignition timing requirements based on these inputs, andcontrols fuel delivery and ignition timing accordingly. TheEngine Control System is comprised of (1) the sensors andswitches that provide input to the PCM, (2) the PCM itself,and (3) the PCM outputs (engine control devices that thePCM constantly adjusts). The Engine Control Systemconsists ofBattery VoltageManifold Absolute Pressure (MAP) SensorCoolant Temperature SensorManifold Air Temperature (MAT) SensorExhaust Oxygen (0,) SensorInduction SystemEngine Speedcrankshaft Position SensorThrottle Position SensorInjector Synchronization SignalA/C Select SignalAIC Request SignalNeutral Safety SwitchKnock SensorFuel Pump RelayFuel InjectorsIdle Speed Stepper MotorB+ Latch RelayOxygen Sensor Heater RelayEGR Valve SolenoidIgnition Control ModuleShift Indicator Light (manual transmissions only)A/C Clutch RelayPowertrain Control Module (PCM)The Powertrain Control Module (PCM) is a digitalmicroprocessor. Air-fuel mixture calibrations for variousdriving and atmospheric conditions are pre-programmedinto the PCM. The PCM monitors and analyzes its variousinputs, computes engine fuel and ignition timingrequirements based on these inputs, and controls fueldelivery and ignition timing accordingly. As operatingconditions change, the PCM adjusts injector pulse width andignition timing for optimum performance and fuel economy.Jeep High Performance ComputerMopar Performance Parts computer provides more sparkadvance and increased fuel flow for off road racingapplications. This computer will enhance otherperformance modifications. For 1987-90, 4.0L enginesonly.P4529334PCM InputsJeep high performance computer.The PCM is powered by the vehicle’s battery. When theignition is turned to the ON or START position, thefollowing inputs are supplied to the PCM:Battery VoltageManifold Absolute Pressure (MAP) SensorCoolant Temperature Sensor