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 operation of thermostatic air cleaner damper door.
• Ensure P/N switch is properly adjusted.
• Check for intermittent open or short to ground in Torque Converter Clutch (TCC) or HEI by-pass circuits.
• Check for proper operation of canister purge system.
• Check for proper operation of ESC system.
• Check for proper operation of EGR system.
• Ensure initial ignition timing is properly set.
• Check for adequate spark output using Spark Tester (ST-125).
• Check oxygen sensor for lead or RTV sealant contamination. This will cause a false high voltage signal to ECM/PCM. ECM/PCM will respond by leaning air/fuel ratio.
• Check in-line fuel filter, and replace if dirty or clogged.
• Check fuel for water contamination. Ensure fuel system pressure is correct at all engine speeds.
• Remove spark plugs and check for wet plugs, cracks, improper gap, burned electrodes or heavy carbon deposits. Also, check condition of distributor cap, rotor and spark plug wires.
• Check charging system output. Repair charging system if voltage is less than 9 volts or more than 17 volts.
• Check A/C for excessive charge.
• Check for restricted exhaust system.
• Ensure driver understands operation of TCC, VCC and A/C. See owner's manual.
• Check speedometer calibration.
• Check for rich or lean conditions. Check fuel system pressure when condition exists. Check for plugged injectors. On MFI vehicles, perform INJECTOR BALANCE TEST in the article SYSTEM/COMPONENT TESTS in the ENGINE PERFORMANCE section.
• Ensure ECM/PCM grounds are clean and tight.
• Check for excessive use of additives in fuel.