Symptom Definition

Engine power varies under steady throttle or cruise. Feels like vehicle speeds up and slows down even though accelerator pedal position remains constant.

Possible Causes & Corrections:

• Ensure park/neutral switch is properly adjusted.
• Check TCC for proper operation.
• Check for restricted exhaust system.
• Check for kinked or leaking vacuum lines.
• Ensure initial ignition timing is properly set.
• Using Spark Tester (ST-125), check for adequate spark output.
• Remove spark plugs, and check for wet plugs, cracks, improper gap, burned electrodes or heavy carbon deposits. Check distributor cap, rotor and spark plug wires.
• Check ESC system for proper operation.
• Check in-line fuel filter. Replace if dirty or clogged.
• Check fuel for water contamination.
• Ensure fuel system pressure is correct at all engine speeds.
• If emission test shows excessive CO and HC emissions and vehicle emits odor, check all systems and components which could cause engine to run rich. See DIAGNOSTIC AIDS in DTC 45 chart in TESTS W/CODES - 4.3L article in the ENGINE PERFORMANCE section.
• If emission test shows excessive NOx emissions, check all systems and components which could cause engine to run lean or too hot. See DIAGNOSTIC AIDS in DTC 44 chart in TESTS W/CODES - 4.3L article in the ENGINE PERFORMANCE section.
• Check canister purge system for proper operation.
• Check for an intermittent EGR system problem.
• Check Oxygen Sensor (O2S) for lead or RTV sealant contamination. Such contamination causes a false high voltage signal to PCM, which responds by leaning air/fuel ratio.
• Check PCM grounds. Ensure they are clean, tight and properly located.
• Check charging system output. Repair if output is less than 9 volts or more than 16 volts.
• Check A/C for excessive charge.