Preliminary Checks

• Verify the on-vehicle diagnostics are working by performing ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in BASIC TESTING article.
• Ensure PCM grounds are clean, tight, and properly located.
• Check vacuum hoses for splits, kinks, leaks, restrictions, and proper connections. Ensure vacuum hoses are correctly routed as shown on Vehicle Emission Control Information label.
• Check for air leaks at all intake manifold sealing surfaces.
• Check ignition wires for cracking, hardness, proper routing and carbon tracking.
• Check wiring for proper connections and routing, pinches, burns, cuts or other damage.
• Ensure PCM and MIL are functioning properly.
• Ensure there are no diagnostic trouble codes stored, or only intermittent codes are present.
• Ensure fuel control system is operating properly. See BASIC TESTING article.
• Perform fuel system pressure test in BASIC TESTING article.
• Perform a careful visual inspection of all systems.

After all checks have been performed, verify customer complaint and locate correct symptom. Check items indicated under that symptom. Not all items listed under each symptom apply to all models and systems. These procedures will normally recommend testing of a specific system or component, such as EGR, ignition, TCC, etc. See SYSTEM/COMPONENT TESTS article for test procedures.