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Diagnosis & Repair

  1. Start engine. If a misfire is present at idle, go to step 3). If no misfire is present, go to next step.
  2. Connect scan tool to DLC. Turn ignition on. Review FREEZE FRAME data. Select CLEAR INFORMATION function. Operate vehicle within FREEZE FRAME conditions. If DTC P0300 resets, go to next step. If DTC P0300 does not reset, check for an intermittent problem. See TESTS W/O CODES article.
  3. Install a spark tester at end of each ignition wire. Crank engine and observe spark tester. If a strong Blue spark is present, go to step 8). If spark is weak or no spark is present, go to next step.
  4. Remove and inspect ignition wires for carbon tracking and insulation damage. Repair as necessary. Retest system. If wires are okay, go to next step.
  5. Remove ignition wire(s) affected by misfire. Using an ohmmeter, measure resistance of each wire in question. Replace ignition wire if resistance is greater than 3.0-6.7 k/ohms per foot. If wires are okay, go to next step.
  6. Inspect distributor cap for moisture, cracks, carbon tracking, or poor terminal connection. Repair as necessary. If cap and rotor are okay, go to next step.
  7. Check signal rotor for damage. Ensure air gap is correct. Repair as necessary. If signal rotor is okay, go to step 12).
  8. Remove and inspect spark plugs. Check for improper gap, cracked ceramic insulators or electrodes. Repair as necessary. If spark plugs are okay, go to next step.
  9. Ensure ignition is off. Install fuel pressure gauge. Note fuel pressure with engine idling at normal operating temperature. If fuel pressure is 13-20 psi (0.9-1.4 kg/cm2 ), go to next step. If fuel pressure is not as specified, go to CIRCUIT TEST A1-7B in BASIC TESTING article.
  10. Check fuel for contamination. Repair as necessary. Retest system. If fuel is okay, go to next step.
  11. Check for an engine mechanical problem. If no mechanical problems are found, see TESTS W/O CODES article.
  12. Check ignition coil for cracks. Using an ohmmeter, measure resistance of ignition coil. Primary resistance should be 1.08-1.32 k/ohms, and secondary resistance should be 22.1-29.9 k/ohms at 68°F (20°C). Replace ignition coil if resistance is not as specified. If ignition coil is okay, see TESTS W/O CODES article.
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