Possible Causes & Corrections
WARNING: This page is about a different car, the 2003 Pontiac Montana, 2003 Oldsmobile Silhouette, and 2003 Chevrolet Venture. However, it is still accessible from the selected car via links, so may be relevant.
Check the following items:
- Fuel system circuits for proper operation. Refer to fuel pump electrical circuit diagnosis in FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 3.4L MONTANA, SILHOUETTE & VENTURE article.
- Low fuel pressure. Refer to FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 3.4L MONTANA, SILHOUETTE & VENTURE article.
- Faulty fuel injectors. Refer to FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 3.4L MONTANA, SILHOUETTE & VENTURE article.
- Fuel contamination.
- Inspect any items which may cause an engine to run rich. Using scan tool, long term fuel trim is significantly in the negative range.
- Inspect any items which may cause an engine to run lean. Using scan tool, long term fuel trim is significantly in the positive range.
- Inspect spark plugs for proper heat range and reach.
- Inspect for proper ignition voltage output using Spark Tester (J-26792).
- If spark is not present at the coils, inspect ignition coil for cracks, carbon tracking/arcing, coil resistance value out of range (5000-8000 ohms). Check spark plug wires for signs of arcing, crossfiring, cracks, carbon tracking, plug boot damage, pinched, improper routing, or a resistance value out of range (3000 ohms per foot). Check for defective ignition module, ignition system wiring, loose ignition module feed or ground connection, or damaged system wiring.
- Remove spark plugs and inspect for fouled plugs, cracks, wear improper gap burned or damaged electrodes improper heat range or reach.
- If spark plugs are gas or oil fouled, the cause of the fouling must be determined before replacing the spark plugs.
- Low engine coolant.
- Restricted air flow to radiator or restricted water flow through the radiator.
- Inoperative electric cooling fan circuits.
- Correct coolant solution should be a 50/50 mix.
- Excessive oil in combustion chamber or leaking valve seals.
- Low cylinder compression.
- Incorrect basic engine parts. Inspect cylinder heads, camshaft, valve train components, pistons, etc.
- Test the CKP sensor "B" for an internal short. Refer to Electronic Ignition System under IGNITION SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 3.4L MONTANA, SILHOUETTE & VENTURE article or see DIAGNOSTIC TROUBLE CODE DEFINITIONS DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 3.4L MONTANA, SILHOUETTE & VENTURE article.
- Test for proper EGR system operation. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 3.4L MONTANA, SILHOUETTE & VENTURE article.
- Inspect the Transaxle Range Switch input with the vehicle in Drive and gear selector in Drive or Overdrive.
- Test the Torque Converter Clutch (TCC) operation. Refer to appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS. TCC applying too soon can cause engine to spark knock.
- If scan tool readings are normal and there are no engine mechanical faults, fill the fuel tank with a known-good quality gasoline that has a minimum octane rating of 87 and re-evaluate vehicle performance.