Possible Causes & Corrections

Check the following items:

• Search for bulletins.
• Verify that PCM grounds are clean, tight and in the proper locations.
• Check fuel system for incorrect fuel pressure. See FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 2.2L SONOMA & S10 PICKUP article.
• Inspect for a contaminated fuel condition.
• Verify that each injector harness is connected to the correct injector or cylinder. Relocate injector harnesses as necessary.
• Inspect Secondary Air Injection (AIR) system. For electric AIR pump testing, perform related DTC testing procedure. See SELF-DIAGNOSTICS - 2.2L SONOMA & S10 PICKUP 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 valve end several times. The valve should snap back. If not, replace PCV.
• Check for adequate ignition coil voltage with a 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 the fouling before replacing the spark plugs.
• Visually and physically inspect secondary ignition for ignition wires arcing to ground or ignition coils arcing to ground.
• Soak 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 - 2.2L SONOMA & S10 PICKUP article.
• Inspect for loose ignition coil grounds.
• Inspect engine coolant level for being low.
• Inspect engine thermostat for proper operation and for correct heat range.
• Check engine compression. A low compression can be caused by sticking or leaking valves, worn camshaft lobes, improper valve timing, bent push rods, worn rocker arms, broken valve springs, excessive oil in combustion chamber or leaking valve seals.
• Check for incorrect basic engine parts. Inspect camshaft, cylinder heads and pistons.
• 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 exhaust system for possible restrictions. Check exhaust system for damaged or collapsed pipes, mufflers for heat distress or possible internal failure or a possible plugged three-way catalytic converters by comparing exhaust system backpressure on each side of engine. Inspect backpressure by removing AIR check valves near exhaust manifolds.
• Inspect intake manifold and exhaust manifold passages for casting flash.