2002 Mercury Villager BaseFACTORY OEM SERVICE PROCEDURE

Test JB: Ignition Misfire Under Load: Testing

  1. 1) Check Firing Order

    Ensure firing order is 1-2-3-4-5-6. Correct firing order if necessary. Reconnect all electrical connections and repeat QUICK TEST . If firing order is okay, go to next step.

  2. 2) Check For Spark At Plugs

    Connect a spark tester at end of spark plug wire and crank engine. Repeat for all spark plugs. If each spark plug wire produces spark and engine starts, go to next step. If each spark plug wire produces a spark and engine is a no-start, go to TEST HC  , step  1). If no spark is produced, go to step  9).
    3. NOTE: If this portion of testing is to provide accurate results, it is essential that calibration of engine analyzer be maintained. Refer to equipment manufacturer's operating manual for procedure to calibrate engine analyzer. If this is not available, an estimate of calibration can be made by connecting spark tester to a properly operating ignition system and measuring firing voltage of spark tester only. DO NOT include firing voltage to cap-to-rotor gap. Spark tester firing voltage should be approximately 28 k/volts plus or minus 10 percent.

  3. 3) Check Secondary Display Average Voltage In Range
    Connect an oscilloscope to engine. Start and operate engine at 2000 RPM. Normal spark output voltage is about 25-31 k/volts. If spark output is not as specified, go to next step. If spark output voltage is as specified, go to step  20).

  4. 4) Check Secondary Display Average Voltage Above Range

    If average spark output voltage is more than 28 k/volts and variation between cylinders is more than 5.6 k/volts, check spark plugs for wear or wide gap at all cylinders. Check for problems that may cause excessive cap-to-rotor gap. Repair as necessary. If average spark output voltage and variation between cylinders is 28 k/volts or less and variation between cylinders is 5.6 k/volts or less, go to next step.

  5. 5) Check Secondary Display For Evenness

    If spark output voltage variation is more than 5.6 k/volts, check spark plugs for wide gaps, worn electrodes, improperly installed cap or rotor, faulty fuel injector or engine mechanical problem; such as bad valves, low compression or vacuum leaks. If spark output voltage variation is 5.6 k/volts or less, go to next step.

  6. 6) Check Secondary Display For High Spark

    If spark output voltage is consistently high only in some cylinder(s), check for defective spark plug or wire. Repair as necessary. If spark output voltage is low, go to next step.

  7. 7) Check Secondary Display For Low Spark

    If spark output voltage is low or spark line slopes downward only in some cylinders, check distributor cap for carbon tracking. Check spark plugs for narrow gap or fouling, and check spark plug wires for grounding. If spark output voltage is not as described, go to next step.

  8. 8) Check Secondary Display For Reversed Voltage

    If oscilloscope displays an upside down firing pattern, replace distributor. Reconnect all electrical connections and repeat QUICK TEST . If firing pattern is not upside down, go to next step.

  9. 9) Check Distributor Assembly

    Check distributor, cap and rotor for wear or damage. Check module for breakage, cracks or oxidation. Ensure rotor turns easily without binding. Replace or service as necessary. If distributor, cap, rotor and module are okay, go to next step.
    10. CAUTION: DO NOT puncture a spark plug wire when measuring resistance. Measure only as directed.
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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.

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