Possible Causes & Corrections

Check the following items:

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• 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 SYSTEMS in SYSTEM & COMPONENT TESTING - 2.2L SONOMA & S10 PICKUP article.
• Inspect for incorrect fuel pressure. See FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 2.2L SONOMA & S10 PICKUP article.
• Inspect for a restricted fuel filter.
• Inspect for a contaminated fuel condition.
• Inspect that each fuel injector harness is connected to the correct injector/cylinder. Relocate fuel injector harnesses as necessary.
• Inspect for the following that may cause the 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, any vacuum hoses that are split, kinked or improperly connected, an air intake duct that is collapsed or restricted, or an air filter that is dirty or restricted.
• Inspect for the following conditions that may cause the engine to run lean: Water intrusion in HO2S connector, exhaust leak between HO2S and engine, vacuum leaks, incorrect fuel pressure, restricted fuel injectors, fuel contamination, or vacuum hoses that are split, kinked or improperly connected.
• Inspect the crankcase ventilation valve for proper operation. Place a finger over the inlet hole of the valve end several times. The valve should snap back. If not, replace PCV.
• Use a scan tool in order to monitor the Knock Sensor (KS) system for excessive spark retard activity.
• If the stalling condition occurs when the A/C is turned on or when transmission is put into gear, make sure that the PCM recognizes the change in state for the component and the Idle Air Control (IAC) counts change accordingly.
• Inspect for proper IAC operation with the scan tool.
• Inspect the Oxygen Sensor No. 1 (O2S 1). The O2S 1 should respond quickly to different throttle positions. If not, inspect the O2S 1 for the silicone or other contaminants from fuel or the use of improper RTV sealant. The sensors may have a White powdery coating. Silicone contamination causes a high but false O2S 1 signal voltage, a rich exhaust indication. The PCM will reduce the amount of fuel delivered to the engine, causing a severe driveability problem.
• Inspect for proper operation of the Manifold Absolute Pressure (MAP) sensor. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 2.2L SONOMA & S10 PICKUP article.
• Inspect for proper operation of the Throttle Position (TP) sensor. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 2.2L SONOMA & S10 PICKUP article.
• Inspect for proper operation of the Engine Coolant Temperature (ECT) sensor. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 2.2L SONOMA & S10 PICKUP article.
• 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 the 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 the 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 mechanical for low compression. Low compression can be caused by sticking or leaking valves, worn camshaft lobes, valve timing, bent push rods, worn rocker arms, or broken valve springs. Check for excessive oil in combustion chamber or leaking valve seals.
• For incorrect basic engine parts, including camshaft, cylinder heads or pistons.
• Inspect the exhaust system for possible restrictions. Inspect for exhaust system for damaged or collapsed pipes. Inspect mufflers for heat distress or possible internal failure. Inspect for possible plugged three-way catalytic converters by comparing exhaust system back pressure on each side of engine. Inspect the back pressure by removing Secondary Air Injection (AIR) check valves near exhaust manifolds.
• 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 the Park/Neutral Position (PNP) switch circuit.
• Inspect for faulty motor mounts.
• Inspect the intake manifold and the exhaust manifold passages for casting flash.