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DTC P0300: Random Misfire Detected

NOTE: Ensure engine compression, valve adjustment and ignition timing are within specifications before proceeding with following test. See BASIC TESTING article. If any DTCs besides DTC P0171, P0172 or P0300-P0304 are set, diagnose them first.
  1. Remove spark plugs and check for proper gap. Check for carbon deposits or cracked insulators. Repair as necessary. Disconnect injector harness connector. Using a spark tester, ensure a strong Blue spark is present at each plug wire. If a strong Blue spark is present at each plug wire, reconnect injector harness connector and go to next step. If no spark or a weak spark is present, check ignition system components. See IGNITION CHECKS in BASIC TESTING article.
  2. Install fuel pressure gauge. Check fuel pressure at specified conditions. See FUEL PUMP PERFORMANCE table. If fuel pressure is as specified, go to next step. If fuel pressure is not as specified, go to CIRCUIT TEST B-3 under CIRCUIT CHECKS in BASIC TESTING article.
    FUEL PUMP PERFORMANCE

    KOEO psi (kg/cm2 ) (1) Engine @ Idle psi (kg/cm2 )
    22.7-29.9 (1.6-2.1) 12.8-20.0 (0.9-1.4)
    (1) Key on, engine off.
  3. Check fuel injector and fuel system circuit. See FUEL SYSTEM in SYSTEM/COMPONENT TESTS article. Repair as necessary. Retest system. If fuel system is okay, go to next step.
  4. Check EGR for proper operation. See EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM/COMPONENT TESTS article. Repair as necessary. If EGR system is okay, go to next step.
  5. Disconnect hose from PCV valve. Start engine and let idle. Check for vacuum at PCV valve. If vacuum is not present, remove PCV valve from intake manifold. If engine runs rough or stalls, replace PCV valve. If engine does not run rough or stall, check for restriction in PCV valve intake passage. Repair as necessary. If PCV system is okay, go to next step.
  6. Turn ignition off. Allow engine to cool. Disconnect purge hose from EVAP canister. Start engine. Place a finger over end of disconnected hose. If no vacuum is present, go to next step. If vacuum is present, check EVAP canister purge valve. Follow procedures in step 3) of DTC P0443  . Repair as necessary. If EVAP canister purge valve is okay, go to next step.
  7. Check MAP sensor performance. See DTC P0106  , step 4). Repair as necessary. If MAP sensor performance is okay, go to next step.
  8. Check ECT sensor performance. See ENGINE SENSORS & SWITCHES in SYSTEM/COMPONENT TESTS article. Repair as necessary. If ECT sensor performance is okay, go to next step.
  9. Check PCM harness connections and grounds for corrosion or lose terminals. Repair as necessary. If connections are okay, check for an intermittent problem. See TESTS W/O CODES article. Repair as necessary. Retest system.
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