GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2001 🢒 Park Avenue 🢒 Engine 🢒 Engine Electrical 🢒 Hesitation, Sag, Stumble

Checks

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 Important Preliminary Checks in Symptoms - Engine Controls .
    • Refer to Visual/Physical Checks in Symptoms - Engine Controls .
    • Search for bulletins.

Sensor/System
    • Check the heated oxygen sensors (HO2S). The heated oxygen sensors 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). The PCM will reduce the amount of fuel delivered to the engine, causing a severe driveability condition.
    • Check the throttle position (TP) sensor and related wiring.
    • Check the mass air flow (MAF) sensor and related wiring.
    • Check the exhaust gas recirculation (EGR) system for proper operation. Refer to Exhaust Gas Recirculation (EGR) System Description .

Fuel System
    • Check the fuel pressure. Refer to Fuel System Diagnosis .
    • Check for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Check items which can cause an engine to run rich, Long Term FT is significantly in the negative range. Refer to Diagnostic Aids for DTC P0171 .
    • Check items that can cause an engine to run lean, Long Term FT is significantly in the positive range. Refer to Diagnostic Aids for DTC P0172 .

Ignition System
    • Check 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 spark tester. Leave the other end of the spark plug wire connected to the coil being tested.
       - Connect another spark plug wire between the remaining tower of the coil being tested and ground.
       - Crank the engine while observing the spark tester, a spark should be observed.
       - Repeat the above steps for each coil.
    • If spark is not present at the coils, check for the following conditions:

   Important: If carbon tracking is detected on a component, replace that component and its mate.

       - Coils--Cracks, carbon tracking/arcing, or a secondary resistance value outside the specified range.

Coil Resistance
5,000-8,000 ohms

       - Spark plug wires--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
9,840 ohms per meter (3,000 ohms per ft)

   Important: Spraying the secondary ignition wires with a light mist of water may help locate an intermittent condition. 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 spark plugs and check for the following:
       - Fouled plugs
       - Cracks

   Important: If carbon tracking is detected on a component, replace that component and its mate.

       - Check the spark plugs for carbon tracking on the porcelain and pitting on the plug wire contact.
       - Improper gap
       - Burned or damaged electrodes
       - Improper heat range or reach
       - Refer to Maintenance Items in Maintenance and Lubrication.
    • If spark plugs are gas or oil fouled, the cause of the fouling must be determined before replacing the spark plugs.