Fuel Injector Balance Test
- Connect fuel pressure gauge to fuel rail. Disconnect vacuum hose at pressure regulator. Turn ignition on. Note fuel pressure. Fuel pressure should be 35-38 psi (2.5-2.7 kg/cm 2 ). Start engine. Reconnect vacuum hose. Fuel pressure should decrease slightly. NOTE: Fuel pressure must be correct before proceeding with fuel injector balance test.
- With ignition off, unplug harness connectors at all injectors. Install Injector Tester (J-34730-3) on one injector. Turn ignition on. Bleed off air in fuel pressure gauge. Fuel pump should operate for about 2 seconds.
- Turn ignition off for 10 seconds. Turn ignition on with engine off. Turn injector on by pressing button on injector tester. Note pressure drop as soon as gauge needle stops. Pressure may increase for a few seconds after initial pressure drop.
- Injector pressure drop should be similar for all injectors. Replace any injector with more than a 1.45 psi (10 kg/cm 2 ) difference from other injectors.
Diagnostic Aids
A slow unstable idle may be caused by a system problem which cannot be overcome by IAC valve. Scan tester counts will be more than 80 counts if too low and zero counts if too high.
If idle is too high, stop engine. Turn ignition on and ground diagnostic test terminal. Wait 30 seconds for IAC valve to seat, then disconnect IAC valve. Remove ground from diagnostic test terminal, and start engine. If idle speed is more than 450 RPM in Drive, locate and correct vacuum leak. If RPM is less than 450 RPM, adjust minimum idle speed or correct other conditions affecting idle speed.
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A slow unstable idle may be caused by a system problem which cannot be overcome by IAC valve. Scan tester counts will be more than 60 counts if too low or zero counts if too high.
Check the following to repair a non-IAC system problem
- Vacuum Leak
- Lean Heated Oxygen Sensor Signal
- Rich Heated Oxygen Sensor Signal
- Throttle Body
- IAC Valve Electrical Connections
- PCV Valve
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If ESC system checks okay but detonation is customer's complaint, refer to TESTS W/O CODES - EFI article.
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If ESC system checks okay but detonation is customer's complaint, refer to TESTS W/O CODES - EFI article.
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Note. If problem develops with EST, ECM will set Code 42. For additional testing, see appropriate SELF-DIAGNOSTICS article.
If EGR system works properly, check for restricted EGR passages or defective MAP sensor. These items could cause high block learn values in open throttle, but not in closed throttle.
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CHART C-10 - A/C CLUTCH CONTROL DIAGNOSIS PICKUP 3.1L
A/C clutch control relay is ECM-controlled to delay A/C clutch engagement approximately .4 second after A/C is turned on. This allows IAC to adjust engine RPM before A/C clutch engages. ECM also causes relay to disengage A/C clutch during WOT, when high power steering pressure is present or if engine is overheating. A/C clutch control relay is energized when ECM provides a ground for Blue/White wire at terminal A2.
Note. Test numbers refer to numbers on diagnostic chart.
- This test checks for low refrigerant or dual pressure switch as cause for no A/C.
- This and following steps check for a faulty A/C control relay.
- This and following steps check for an open in ECM wiring or a faulty ECM.
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CHART C-10 - A/C CLUTCH CONTROL DIAGNOSIS RODEO 3.2L & TROOPER
Note. Corresponding ECM terminal for Rodeo and trooper is C9.
When A/C is turned on, ECM supplies ground for A/C control relay. Battery voltage is supplied to A/C clutch solenoid through thermoswitch relay. This relay is part of A/C on/off switch circuit. If A/C system exhibits high pressure or overheating condition, system will be turned off by A/C high pressure safety switch or by A/C thermoswitch circuit.
- A/C high pressure switch is located in high pressure hose.
- Thermoswitch is part of A/C evaporator mounted under dash.
