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:

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Test the 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.
Test for low fuel pressure. Refer to FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 3.4L MONTANA, SILHOUETTE & VENTURE article.
Test for faulty fuel injectors. Refer to FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 3.4L MONTANA, SILHOUETTE & VENTURE article.
Inspect for fuel contamination.
Inspect for fuel in the pressure regulator vacuum hose.
Ensure each injector harness is connected to the correct injector/cylinder.
Inspect for any items which may cause an engine to run rich. Using scan tool, long term fuel trim is significantly in the negative range.
Inspect for any items which may cause an engine to run lean. Using scan tool, long term fuel trim is significantly in the positive range.
Test for conditions which cause an incorrect idle speed. Check for throttle body tampering, excessive deposits or damage. Check for restricted air intake system or large vacuum leak.
Inspect the air intake ducts for being collapsed, damaged areas, looseness, improper installation, or leaking especially between the MAF sensor and the throttle body.
Inspect crankcase ventilation valve for proper operation. See EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - 3.4L MONTANA, SILHOUETTE & VENTURE article.
Inspect the Throttle Position (TP) sensor and related wiring. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 3.4L MONTANA, SILHOUETTE & VENTURE article.
Monitor the 24X crank sensor and CMP sensor signal present parameters on scan tool. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 3.4L MONTANA, SILHOUETTE & VENTURE article. If both are not responding, test the sensor feed circuit. Both sensors use a separate feed circuit but are internally connected to power. Test all CKP sensor "A" and CMP sensor circuits for intermittents.
Monitor the 3X parameter on the scan tool. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 3.4L MONTANA, SILHOUETTE & VENTURE article. If the 3X is not responding, inspect the CKP sensor "B" and circuits for intermittents. Inspect the Ignition Control (IC) circuit, IC timing control circuit, low resolution engine speed signal circuit and the low reference circuit for intermittents. If these circuits become open or shorted, they may not set a DTC immediately, but are capable of causing driveability complaints.
Test EGR system for proper 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 the gear selector in Drive or Overdrive.
Inspect for proper ignition voltage output using Spark Tester (J-26792).
If spark is not present at the coils, inspect coils for cracks, carbon tracking/arcing, or a resistance value outside the specified 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 outside the specified 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.
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, which can be caused by leaking valve seals.
For incorrect basic engine parts, such as camshaft, cylinder heads, pistons, etc.
Inspect exhaust system for damaged or collapsed pipes.
Inspect mufflers for heat distress or possible internal failure.
For possible plugged three-way catalytic converter.
An engine miss condition can be caused by Electromagnetic Interference (EMI) on the reference circuit. EMI can usually be detected by monitoring engine RPM with a scan tool. A sudden increase in RPM with little change in actual engine RPM change, indicates EMI is present. If a problem exists, inspect the routing of secondary ignition wires, high voltage components, e.g. near ignition control circuits.
Inspect for intake and exhaust manifold passages for casting flash.