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.
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HOMESERVICE MANUALSMERCURY1998MOUNTAINEER 5.0 P, AWDREPAIR AND DIAGNOSISENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS - TESTS W/CODES - 5.0LCIRCUIT TESTSCIRCUIT TEST JB - SECONDARY IGNITION
1998 Mercury Mountaineer 5.0 P, AWD
Circuit Test JB - Secondary Ignition
1998 Mercury Mountaineer 5.0 P, AWDSECTION Circuit Test JB - Secondary Ignition
NOTE:
After each service or repair procedure has been completed, reconnect all components. Clear DTCs and repeat QUICK TEST
procedures to ensure all EEC-V systems are working properly and DTCs are no longer present.
- 1) Preliminarily Test
Ensure battery is fully charged and all accessories are off. Check all wiring harnesses and connectors for damage, and burned or overheated insulation. Repair as necessary. Perform MISFIRE MONITOR REPAIR VERIFICATION DRIVE CYCLE. See DRIVE CYCLES under ADDITIONAL SYSTEM FUNCTIONS. If no problems are found, go to next step (models equipped with coil pack). - 2) Connect Engine Analyzer
DTC P0350 indicates an ignition coil primary circuit malfunction. Install Rotunda Engine Analyzer (010-00869) engine analyzer. If vehicle has a no-start condition, go to next step. If vehicle starts, go to step 4). - 3) Check For Normal Ignition Pattern
Crank engine and observe scope pattern. If scope pattern is normal, go to CIRCUIT TEST A , step 7). If scope pattern is not normal, repair IGN START run circuit (no-start condition) or go to next step (if vehicle starts). - 4) Check For Normal Ignition Operation
Start engine. Select Multi-Strike operating mode on engine analyzer. Multi-Strike operating mode is dependent on PCM calibration and is limited to less than 2000 RPM. Observe scope pattern and check average spark output voltage and variation of pattern. If average spark output firing voltage is 20,000 or less with output variation 8000 volts or less, no problem is indicated at this time. Testing is complete. If DTCs P0300-P0310 are present, check fuel pressure. See CIRCUIT TEST HD , step 5). If directed here from TESTS W/O CODES - EEC-V article, return to symptom test that directed you here. On all others, go to CIRCUIT TEST Z . If spark output voltage is not as specified, go to next step (models equipped with coil pack). - 5) Check Spark Voltage
Check spark output voltage for all cylinders. If average spark output voltage is more than 20,000 volts with spark output variation less than 8000 volts, check spark plugs for wear and spark plug wires for 7000 ohms per foot maximum resistance. Repair as necessary. Perform MISFIRE MONITOR REPAIR VERIFICATION DRIVE CYCLE. See DRIVE CYCLES under ADDITIONAL SYSTEM FUNCTIONS. If spark output voltage is not as specified, go to next step. - 6) Check For Voltage Variation Between Cylinders
If spark output voltage variation is more than 8000 volts, check spark plugs for wide gap or worn electrode. Repair as necessary. Perform MISFIRE MONITOR REPAIR VERIFICATION DRIVE CYCLE. See DRIVE CYCLES under ADDITIONAL SYSTEM FUNCTIONS. If spark output voltage variation is less than 8000 volts, go to next step. - 7) Check For High Spark Voltage
If spark output voltage is consistently high in one or more cylinders, check for defective spark plug or wire. Perform MISFIRE MONITOR REPAIR VERIFICATION DRIVE CYCLE. See DRIVE CYCLES under ADDITIONAL SYSTEM FUNCTIONS. If spark output voltage is not consistently high in one or more cylinders, go to next step. - 8) Check For Low Spark Voltage
If spark output voltage is consistently low in one or more cylinders, go to next step. If spark output voltage is not consistently low in one or more cylinders, proceed as follows:- If DTCs P0300-P0310 are present, go to CIRCUIT TEST HD , step 5).
- If directed here from TESTS W/O CODES - EEC-V article, return to symptom test that directed you here.
- 9) Check For Missing Spark Patterns
If spark is not missing from 2-cylinders on same coil, go to CIRCUIT TEST JE . If spark is missing from 2-cylinders on same coil, check spark plugs for wear and spark plug wires for 7000 ohms per foot maximum resistance. Repair as necessary and retest. If plug wires and plugs are okay, go to CIRCUIT TEST JE.NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 9) to step 12). No test procedures have been omitted. - 12) Check For High Spark Voltage
Observe scope pattern and check average spark output voltage and variation of pattern. If average spark output firing voltage is more than 20,000 with output variation 8000 volts or less, check spark plugs for wear. Check ignition coil for proper installation. Repair as necessary. Perform MISFIRE MONITOR REPAIR VERIFICATION DRIVE CYCLE. See DRIVE CYCLES under ADDITIONAL SYSTEM FUNCTIONS. If spark output voltage is not as specified, go to next step. - 13) Check For Voltage Variation Between Cylinders
If spark output voltage variation is more than 8000 volts, check spark plugs for wide gap or worn electrode. Repair as necessary. Perform MISFIRE MONITOR REPAIR VERIFICATION DRIVE CYCLE. See DRIVE CYCLES under ADDITIONAL SYSTEM FUNCTIONS. If spark output voltage variation is less than 8000 volts, go to next step. - 14) Check For High Spark Voltage
If spark output voltage is consistently high in one or more cylinders, ignition coils are not firmly connected. Check ignition coil installation. Perform MISFIRE MONITOR REPAIR VERIFICATION DRIVE CYCLE. See DRIVE CYCLES under ADDITIONAL SYSTEM FUNCTIONS. If spark output voltage is not consistently high in one or more cylinders, go to next step. - 15) Check For Low Spark Voltage
If spark output voltage is consistently low in one or more cylinders, go to next step. If spark output voltage is not consistently low in one or more cylinders, proceed as follows:- If DTCs P0300-P0310 are present, go to CIRCUIT TEST HD , step 5).
- On all others, identify symptom and go to TESTS W/O CODES - EEC-V article.
NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 15) to step 22). No test procedures have been omitted. - 22) Check Spark Quality
With spark tester installed, crank engine and observe color of spark for each cylinder. If spark strong (Bluish/White), go to next step. If spark is not strong, replace ignition coil. Perform MISFIRE MONITOR REPAIR VERIFICATION DRIVE CYCLE. See DRIVE CYCLES under ADDITIONAL SYSTEM FUNCTIONS. - 23) Check Spark Plugs
Remove and inspect spark plugs for damage and wear. If spark output voltage is not as specified, go to next step. Replace plugs as necessary. Perform MISFIRE MONITOR REPAIR VERIFICATION DRIVE CYCLE. See DRIVE CYCLES under ADDITIONAL SYSTEM FUNCTIONS. If spark plugs are okay, proceed as follows:- If sent here from CIRCUIT TEST HD, step 4), go to CIRCUIT TEST HD , step 5).
- If directed here from TESTS W/O CODES - EEC-V article, return to symptom test that directed you here.
- On all other models, go to CIRCUIT TEST Z .
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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.