Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Diagnostic Procedures
- Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 1.8L VIBE article.
- Connect scan tool. Check engine coolant temperature. Is the engine coolant temperature outside 50-95°F (10-35°C)? If yes, go to next step. If no, go to FUEL INJECTOR COIL TEST - ENGINE COOLANT TEMPERATURE BETWEEN 50-95°F (10-35°C) .
- Turn ignition switch to OFF position. To prevent flooding of a single cylinder and possible engine damage, relieve fuel pressure. See FUEL SYSTEM PRESSURE RELEASE
. Connect the Fuel Injector Tester (J 39021), or equivalent, to battery voltage and ground. Set the amperage supply selector switch on the fuel injector tester to the COIL TEST 0.5 AMP position. Connect leads from a DMM to the fuel injector tester. See Figure
. Set DMM to the tenths scale (0.0). Disconnect fuel injector harness connector. Use 2 jumper wires from the Connector Test Adapter Kit (J 35616-A), or equivalent, connect the fuel injector to the J 39021 tester leads.
Check the engine coolant temperature again to ensure that the correct chart is being used. Press the PUSH TO START TEST button on the fuel injector tester. Observe the voltage reading on the DMM. The voltage reading may rise during the test. Record the lowest voltage observed after the first second of the test. Repeat procedure for each fuel injector. Identify the highest voltage reading recorded other than those more than 9.5 volts. Subtract any other voltage reading recorded from the highest voltage reading recorded. Repeat for all remaining injectors. Is any value that resulted from the subtraction more than one volt? If yes, go to next step. If no, go to FUEL INJECTOR BALANCE TEST WITH SPECIAL TOOL .
- Replace any fuel injector that had a subtracted value exceeding 0.6 volt, an initial reading of more than 9.5 volts or an erratic reading. After repair, go to FUEL INJECTOR BALANCE TEST WITH SPECIAL TOOL .
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.