Possible Causes & Corrections

Check for the following items:

• Search for bulletins.
• Inspect PCM grounds for being clean, tight, and in the proper locations.
• Verify the driver understands the operation of the transmission Torque Converter Clutch (TCC) and A/C compressor operation as explained in the owner's manual. Inform the customer how the TCC and the A/C clutch operates.
• Inspect the HO2S. The HO2S should respond quickly to different throttle positions. If they do not, inspect the HO2S for silicone or other contaminates from fuel or use of improper RTV sealant. The sensors may have a White powdery coating and result in a high but false signal voltage rich exhaust indication. PCM will then reduce the amount of fuel delivered to the engine causing a severe driveability problem.
• Inspect Crankshaft Position (CKP) sensor active counter for steady count. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 2.2L SONOMA & S10 PICKUP article.
• Inspect for proper operation of 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.
• Test 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.
• Verify that each injector harness is connected to the correct injector or cylinder. Relocate 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, any vacuum leaks, incorrect fuel pressure, restricted fuel injectors, fuel contamination, or vacuum hoses that are split, kinked or improperly connected.
• 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.
• Test for proper ignition voltage output with Spark Tester (J-26792).
• Remove the spark plugs and inspect for correct heat range, 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.
• Monitor the Misfire Current Counters while driving the vehicle within the conditions that the misfire occurred. If a misfiring cylinder can be located, use the DTC P0300 test procedures for diagnosis. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 2.2L SONOMA & S10 PICKUP article.
• Inspect for loose ignition coil grounds.
• Inspect exhaust system for a possible restriction.
• Inspect exhaust system for damage.
• Visually and physically inspect vacuum hoses for splits, kinks, and proper connections and routing as shown on the underhood Vehicle Emission Control Information label.
• Check TCC operation. A TCC applying too soon can cause spark knock. See appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS.