Hesitation, Sag, Stumble

WARNING: This page is about a different car, the 2010 Pontiac G5 and 2010 Chevrolet Cobalt. However, it is still accessible from the selected car via links, so may be relevant.

Test the fuel pressure. Refer to Fuel System Diagnosis (NT7, NU1) or Fuel System Diagnosis (NU6) .
Inspect the mass air flow (MAF) sensor for contamination and damage. Refer to Mass Airflow Sensor with Intake Air Temperature Sensor Replacement .
Test the generator. Refer to Symptoms - Engine Electrical . Repair the charging system if the generator output voltage is less than 9 V or more than 16 V.
Inspect for excessive crankshaft endplay that will cause the crankshaft position sensor reluctor wheel to move out of alignment with the crankshaft position sensor. Refer to Crankshaft and Bearing Cleaning and Inspection .

NOTE: The following actions may need to be repeated in order to verify an intermittent intake or exhaust camshaft actuator condition.

Engine warm and idling, verify the correct operation of the camshaft actuator system. Command the intake and exhaust camshaft actuators from 0-25 degrees and back to zero while observing the scan tool Int. CMP Variance and Exh. CMP Variance parameters. Each parameter should be less than 2 degrees in each of the commanded states.
- If any of the parameters is greater than 2 degrees, inspect the suspect camshaft actuator and camshaft actuator solenoid valve and valve bore for contamination, obstruction, and damage. Refer to Camshaft Position Actuator Solenoid Valve Replacement and Camshaft Actuator System Description .
Test the manifold absolute pressure (MAP) sensor. Refer to DTC P0106 .