Symptom Checks

Check the following items:

• Check secondary ignition system. Go to TEST JB, step 1)  under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - CNG & GASOLINE article.
• Check fuel delivery system. On Natural Gas models, go to TEST HB, step 1)  under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - CNG & GASOLINE article. On all other models, go to TEST HC, step 1)  under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - CNG & GASOLINE article.
• Check exhaust system for restriction. Go to TEST HF, step 1)  under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - CNG & GASOLINE article.
• Check PCV system. Go to TEST HG, step 1)  under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - CNG & GASOLINE article.
• Check EVAP emission system for blockages (engine stalls) or leaks (excessive fuel odor). Service appropriate symptom under SYSTEM TESTS (EVAPORATIVE EMISSIONS) in SELF-DIAGNOSTICS - EEC-V - CNG & GASOLINE article.
• Check air intake system. Go to TEST HU, step 1)  under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - CNG & GASOLINE article.
• Check starting system. See appropriate STARTERS article in STARTING & CHARGING SYSTEMS.
• Check for contaminated Mass Airflow (MAF) sensor. If MAF sensor is okay, return to SYMPTOM DIAGNOSIS  to identify any additional symptoms or go to TEST Z under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - CNG & GASOLINE article and check for intermittent faults.
• On F150 Lightning Pickup (5.4L Supercharged) models, check high speed fuel pump secondary circuits. Go to TEST KA, step 70)  under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - CNG & GASOLINE article.