Possible Cause & Correction

Check the following items:

• Visually check vacuum hoses for splits, kinks and proper connections as shown on vehicle emission control information label.
• Check for dirty or clogged air filter.
• Check coolant level. Check engine cooling system thermostat for proper heat range and operation.
• Check engine compression. Check for incorrect valve timing, bent push rods, broken valve springs or worn camshaft lobes.
• Check Engine Coolant Temperature (ECT) sensor for shift in calibration. See appropriate SENSOR OPERATING RANGE CHARTS article.
• Check A/C for "full time" operation.
• Ensure initial ignition timing is properly set, and check for proper operation of ignition control and knock sensor systems.
• Check Torque Converter Clutch (TCC) for proper operation.
• Check air intake system and crankcase for air leaks.
• Check exhaust system for restrictions, such as a damaged or collapsed pipe, muffler or catalytic converter.
• Check Heated Oxygen Sensor (HO2S) for silicone or lead contamination.
• Check for proper ignition voltage output. Check the ignition coils for cracks, or damage.
• Remove spark plugs and check for wet plugs, cracks, improper gap, burned electrodes or heavy carbon deposits.
• Ensure speedometer is properly calibrated.
• Check fuel pressure. See FUEL SYSTEM PRESSURE TEST under BASIC FUEL SYSTEM CHECKS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
• Check for poor quality or alcohol contaminated fuel.
• Check fuel injectors. Perform injector balance test. See FUEL INJECTOR BALANCE TEST under FUEL SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article.
• Check injector harness locations. Ensure injectors are connected to correct injector/cylinder according to firing order.
• Check for fuel in pressure regulator vacuum hose. If fuel is present, replace regulator.
• Check Camshaft Position (CMP) and Crankshaft Position (CKP) sensors for proper operation.
• Check for air leaks between Mass Airflow (MAF) sensor and throttle body. Check air induction system for damage, restriction or air leaks.
• Check boost control system (if equipped).
• Check engine compression.
• Check the exhaust system for possible restrictions.
• Check for dragging brakes.
• Check for conditions that cause the engine torque management system to reduce engine power.
• Check for incorrect tire pressure.
• Check for uneven or excessive tire wear from suspension misalignment.
• Check with operator to see if vehicle is operated under excessive acceleration or is heavily loaded.