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.
- Remove and inspect the air filter element for dirt or for restrictions.
- Inspect fuel injectors. See FUEL INJECTOR COIL TEST under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
- Check 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 for a contaminated fuel condition.
- Ensure that each fuel injector harness is connected to the correct injector/cylinder. Relocate fuel injector harnesses as necessary.
- Inspect cause for engine to run rich: Water intrusion in HO2S connector, engine oil contaminated by fuel, EVAP canister purge condition, incorrect fuel pressure, leaking fuel pressure regulator, leaking fuel injectors, inaccurate MAF sensor, blockage on MAF sensor inlet screen, vacuum hoses that are split, kinked or improperly connected, air intake duct that is collapsed or restricted or air filter that is dirty or restricted.
- Inspect cause for engine to run lean: Water intrusion in HO2S connector, exhaust leak between HO2S and engine, vacuum leaks, incorrect fuel pressure, restricted fuel injectors, inaccurate MAF sensor, fuel contamination, or vacuum hoses that are split, kinked or improperly connected.
- Inspect crankcase ventilation valve for proper operation. See EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
- Use a scan tool in order to monitor the Knock Sensor (KS) system for excessive spark retard activity.
- Inspect for proper ignition voltage output with Spark Tester (J-26792).
- Remove spark plugs and check for wet plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits.
- An improper spark plug gap will cause a driveability problem. Gap spark plugs using a wire gauge gap tool.
- Determine the cause of fouling before replacing spark plugs.
- Visually and physically inspect secondary ignition for ignition wires arcing to ground or ignition wires for proper routing.
- 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 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 DTC P0300 in 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 mechanical for compression, sticking or leaking valves, worn camshaft lobes, valve timing, bent push rods, worn rocker arms, broken valve springs or excessive oil in combustion chamber, caused by 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.
- Inspect for incorrect basic engine parts. Inspect camshaft, cylinder heads, pistons, etc.
- Inspect for excessive crankshaft end play that will cause the CKP sensor reluctor wheel to move out of alignment with the CKP sensor. This could result in a no-start, a start and stall or an erratic performance.
- Inspect the exhaust system for possible restrictions. Inspect for damaged or collapsed pipes. Inspect 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 the engine RPM. A sudden increase in RPM with little change in actual engine RPM change indicates that EMI is present. If a problem exists, inspect routing of secondary ignition wires or high voltage components near the ignition control circuits.
- Inspect Park/Neutral Position (PNP) switch circuit.
- Inspect for faulty motor mounts.
- Inspect intake and exhaust manifold passages for casting flash.
- Inspect for a stuck open EGR valve or EGR pintle not seating properly. Inspect EGR valve gasket for leaks.