GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2000 🢒 Regal (China) 🢒 Engine 🢒 Engine Controls - 2.5L (LB8) and 3.0L (L46) 🢒 Hesitation, Sag, Stumble

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Action

DEFINITION: Momentary lack of response as the accelerator is pushed down. Can occur at any vehicle speed. Usually more pronounced when first trying to make the vehicle move, as from a stop sign. May cause the engine to stall if severe enough.

Preliminary
    •  Refer to Intermittent Conditions .
    •  Search for bulletins.

Sensor/System
    • Inspect the heated oxygen (HO2S) sensors. The HO2S should respond quickly to different throttle positions. If not, check the HO2S for silicon or other contaminants from fuel or use of improper RTV sealant. The sensors may have a white powdery coating. Silicon contamination causes a high but false HO2S signal voltage (rich exhaust indication). Refer to

Notice: Contamination of the oxygen sensor can result from the use of an inappropriate RTV sealant (not oxygen sensor safe) or excessive engine coolant or oil consumption. Remove the HO2S and visually inspect the portion of the sensor exposed to the exhaust stream in order to check for contamination. If contaminated, the portion of the sensor exposed to the exhaust stream will have a white powdery coating. Silicon contamination causes a high but false HO2S signal voltage (rich exhaust indication). The control module will then reduce the amount of fuel delivered to the engine, causing a severe driveability problem. Eliminate the source of contamination before replacing the oxygen sensor.

. The PCM will reduce the amount of fuel delivered to the engine, causing a severe driveability problem.
    •  Inspect for 24X crankshaft position (CKP) and camshaft position (CMP) sensors on the scan tool. If both are not responding, check the sensor feed circuit.
    •  Check the TP sensor and related wiring.
    •  Check the MAF sensor and related wiring.
    •  Check the EGR system for proper operation. Refer to Exhaust Gas Recirculation (EGR) System Description .

Fuel System
    • Inspect the fuel pressure. Refer to Fuel System Pressure Test .
    • Inspect for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    •  Inspect items which can cause an engine to run rich (long term fuel trim is significantly in the negative range). Refer to Diagnostic Aids in DTC P0172 Fuel Trim System Rich .
    • Inspect items that can cause an engine to run lean (long term fuel trim is significantly in the positive range). Refer to Diagnostic Aids in DTC P0171 Fuel Trim System Lean .

Ignition System
    • Inspect for proper ignition voltage output using the following steps:
       -  Clip the J 26792 spark tester to engine ground.
       -  Connect one end of a spark plug wire to the J 26792 spark tester. Leave the other end of the spark plug wire to the coil being tested.
       -  Connect one end of another spark plug wire to the other coil tower. Connect the other end of the spark plug wire to ground.
       -  Crank the engine while observing the J 26792 spark tester. A spark should be observed.
       -  Repeat the above steps for each coil.
    •  If spark is not present at the plugs, inspect for the following conditions:
       -  Inspect the coils for cracks, carbon tracking/arcing or a resistance value outside the specified range.

Coil Resistance
5K-7K ohms (5,000-7,000 ohms).

       -  Inspect the spark plug wires for signs of arcing/cross firing, cracks, carbon tracking, plug boot damage, pinched, improper routing or a resistance value outside the specified range.

Spark Plug Wire Resistance
1 968 ohms per meter (600 ohms per foot).

    Important: :  Spraying the secondary ignition wires with a light mist of water may help locate an intermittent problem. Ignition components will arc to ground when a secondary component is faulty.

       -  Defective module
       -  Ignition System Wiring--Loose ignition module feed or ground connection, or damaged system wiring
    •  Remove the spark plugs and inspect for the following:
       -  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.