Possible Causes & Corrections
WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2003 GMC Yukon XL, 2003 GMC Sierra, 2003 GMC Cab & Chassis Sierra, 2003 Chevrolet Suburban, and 2003 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
Check the following items:
- Search for bulletins.
- Verify that PCM grounds are clean, tight, and in the proper locations.
- Inspect for incorrect fuel pressure. See FUEL SYSTEM PRESSURE TEST under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
- Inspect for a restricted fuel filter.
- Inspect fuel injectors. See FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
- Verify that each injector harness is connected to the correct injector or cylinder. Relocate injector harnesses as necessary.
- Inspect Secondary Air Injection (AIR) system. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
- Inspect air intake system and crankcase for air leaks.
- Inspect crankcase ventilation valve for proper operation. Place a finger over the inlet hole in the valve end several times. The valve should snap back. If not, replace PCV valve.
- Inspect for an inaccurate speedometer.
- Use a scan tool in order to monitor the Knock Sensor (KS) system for excessive spark retard activity.
- Inspect for proper ignition voltage output using Spark Tester (J-26792).
- Remove spark plugs and inspect for wet plugs, cracks, wear, improper gap, burned electrodes or heavy deposits.
- An improper spark plug gap will cause a driveability problem.
- Determine cause of fouling before replacing spark plugs.
- Visually and physically inspect secondary ignition for ignition wires arcing to ground or ignition coils arcing to ground.
- Soak the secondary ignition system with water from a spray bottle. Soaking the secondary ignition system may help locate damaged or deteriorated components. Look and listen for arcing or misfiring as you apply the water.
- Monitor the Misfire Current Counters while driving the vehicle in the conditions that the misfire occurred. If a misfiring cylinder can be located, use DTC P0300 diagnostic procedures for diagnosis. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
- Inspect for loose ignition coil grounds. See ELECTRONIC IGNITION SYSTEM DIAGNOSIS under IGNITION SYSTEMS in SYSTEM & COMPONENT TESTING - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
- Inspect engine for low coolant level.
- Inspect engine thermostat for proper operation and for correct heat range.
- Inspect engine mechanical for compression, worn camshaft lobes, valve timing, bent push rods, worn rocker arms, broken valve springs, excessive oil in combustion chamber or leaking valve seals. See CYLINDER COMPRESSION PRESSURE under MECHANICAL INSPECTION under PRELIMINARY INSPECTION & ADJUSTMENTS in BASIC DIAGNOSTIC PROCEDURES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
- For incorrect basic engine parts. Inspect camshaft, cylinder heads, pistons, etc.
- Visually and physically inspect the vacuum hoses for splits, kinks, and proper connections and routing as shown on the underhood Vehicle Emission Control Information label.
- Inspect intake manifold and exhaust manifold passages for casting flash.
- Inspect the transmission Torque Converter Clutch (TCC) operation. See appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS. The scan tool should indicate an RPM drop when TCC is commanded ON.
- Inspect exhaust system for possible restrictions. Inspect exhaust system for damaged or collapsed pipes. Inspect the mufflers for heat distress or possible internal failure. Inspect for possible plugged catalytic converters.
- Electromagnetic Interference (EMI) on the reference circuit can cause an engine miss condition. A scan tool can usually detect EMI by monitoring engine RPM. A sudden increase in RPM with little change in actual engine RPM change may indicate that EMI is present. If a problem exists, inspect for high voltage components near ignition control circuits.
- Inspect Park/Neutral Position (PNP) switch operation.
- Inspect for faulty motor mounts.
- Inspect intake and exhaust manifold passages for casting flash.