Possible Causes & Corrections

Check the following items:

• Compare customer vehicle with a similar unit. Verify the customer's concern.
• Remove air filter and check for dirt or a restriction.
• Inspect transmission shift pattern and downshift operation.
• Inspect for a restricted fuel filter, contaminated fuel, or improper fuel pressure. See FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 4.3L ASTRO, BLAZER, JIMMY CANADIAN, SAFARI, SONOMA & S10 PICKUP article.
• Perform the fuel injector balance test. See FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 4.3L ASTRO, BLAZER, JIMMY CANADIAN, SAFARI, SONOMA & S10 PICKUP article.
• Inspect exhaust system for a possible restriction. See EXHAUST SYSTEM BACKPRESSURE under MECHANICAL INSPECTION under PRELIMINARY INSPECTION & ADJUSTMENTS in BASIC DIAGNOSTIC PROCEDURES - 4.3L ASTRO, BLAZER, JIMMY CANADIAN, SAFARI, SONOMA & S10 PICKUP article.
• Inspect exhaust system for damaged or collapsed pipes. Inspect the muffler for heat distress or a possible internal failure.
• Inspect control module grounds for being clean, tight, and in their proper location.
• Inspect Torque Converter Clutch (TCC) operation. See appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS.
• Inspect A/C operation. See appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING.
• Test generator output voltage.
• Monitor Knock Sensor (KS) system for retarded timing.
• Engine compression. Low compressions can be caused by faulty valve timing or improper or worn camshaft.