Symptom Definition

Engine power varies under steady throttle or cruise. Feels like vehicle speeds up and slows down without changing position of accelerator pedal.

Possible Cause & Correction Check the following:

• Check operation of thermostatic air cleaner damper door.
• Ensure park/neutral 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 O2 sensor for lead or RTV sealant contamination. This will cause a false high voltage signal to ECM. ECM 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 A/C for excessive charge.
• Check for restricted exhaust system.