Symptom Checks

Check the following items:

• Check cooling system for overheating. If cooling system is overheating, go to ENGINE RUNS HOT symptom.
• Check engine mechanical condition. Check compression, camshaft, valve train components, etc.
• Check fuel delivery system. See CIRCUIT TEST HC in appropriate article:

  For 2.5L vehicles, see TESTS W/CODES - 2.5L .

  For 3.0L vehicles, see TESTS W/CODES - 3.0L .

  For 4.0L vehicles, see TESTS W/CODES - 4.0L .

• Check secondary ignition system. See CIRCUIT TEST JB in appropriate TESTS W/CODES article.
• Check PCV system. See CIRCUIT TEST HB in appropriate article:

  For 2.5L vehicles, see TESTS W/CODES - 2.5L .

  For 3.0L vehicles, see TESTS W/CODES - 3.0L .

  For 4.0L vehicles, see TESTS W/CODES - 4.0L .

• On vehicles with OCT ADJ circuit (PCM terminal No. 30), check octane adjust input to PCM. See CIRCUIT TEST FG, step 5) in appropriate TESTS W/CODES article.
• On vehicles with Knock Sensor (KS), check KS input to PCM. See CIRCUIT TEST DG in appropriate article:

  For 2.5L vehicles, see TESTS W/CODES - 2.5L .

  For 3.0L vehicles, see TESTS W/CODES - 3.0L .

  For 4.0L vehicles, see TESTS W/CODES - 4.0L .

• Check intake air system. Check engine oil quality. If available, check Technical Service Bulletins (TSBs) for octane adjust information. If no problems are indicated, return to SYMPTOM DIAGNOSIS  to identify any additional symptoms or go to CIRCUIT TEST Z in appropriate TESTS W/CODES article and check for intermittent faults.