Surges/Chuggles. Buick Roadmaster 1996

For 1990-2009 cars

Checks | Action
--- | ---
DEFINITION: Engine power variation under steady throttle or cruise. Feels like the vehicle speeds up and slows down with no change in the accelerator pedal.

Preliminary

• | Refer to Symptoms , Important Preliminary Checks Before Starting.

• | Search for bulletins.

• | Check PCM grounds for being clean, tight and in their proper locations. Refer to PCM wiring diagrams in Electrical Diagnosis.

• | Be sure driver understands transmission torque converter clutch, and A/C compressor operation as explained in the owners manual. Inform customer how TCC and the A/C clutch operates.

Sensor/System

• | Check Heated Oxygen Sensors (HO2S). The Heated Oxygen Sensors (HO2S) should respond quickly to different throttle position, if they do not, check the HO2S for silicon or other contaminates from fuel, or use of improper RTV sealant. The sensors may have a white powdery coating and result in a high but false signal voltage (rich exhaust indication). The PCM will then reduce the amount of fuel delivered to the engine causing a severe driveability problem. For more information, refer to Powertrain Control Module (PCM) .

• | Check MAF connections. Repair or replace terminals. Refer to Electrical Diagnosis for wiring repair procedures.

• | Check the EGR system for proper operation.

Fuel System

• | Check for low fuel pressure. Refer to Fuel System Diagnosis .

• | Check for restricted fuel filter. Refer to Fuel System Diagnosis .

• | Check for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Test .

• | Check each injector harness is connected to the correct injector/cylinder according to the firing order (firing order: 1-8-4-3-6-5-7-2). Relocate injector harnesses as necessary.

• | Check items which can cause an engine to run rich (long term fuel trim near -14%). For a rich condition, refer to DTC P0132 HO2S Circuit High Voltage Bank 1 Sensor 1 and DTC P0152 HO2S Circuit High Voltage Bank 2 Sensor 1 .

• | Check items that can cause an engine to run lean (long term fuel trim near 22%). For a lean condition, refer to DTC P0131 HO2S Circuit Low Voltage Bank 1 Sensor 1 and DTC P0151 HO2S Circuit Low Voltage Bank 2 Sensor 1 .

Ignition System

• | Wetting down the secondary ignition system with water from a spray bottle may help locate damaged or deteriorated components. Look/listen for arcing or misfiring as water is applied.

• | Check for proper ignition voltage output with spark tester J 26792. Refer to Distributor Ignition (DI) System Check .

• | Remove spark plugs and check for the following:

- | Wet plugs

- | Cracks

- | Wear

- | Improper gap

- | Burned electrodes

- | Heavy deposits

• | An improper spark plug gap will cause a driveability problem. Refer to Spark Plug Gap specification is Section OB . The spark plug gapping should be done using a wire gauge gap tool (J 41319). Refer to Spark Plug Replacement. If spark plugs are gas or oil fouled, the cause of the fouling must be determined before replacing the spark plugs. Refer to DTC P0172 Fuel Trim System Rich Bank 1 and DTC P0175 Fuel Trim System Rich Bank 2 to determine the rich condition or Engine Mechanical for the oil fouling condition.

• | Check for loose ignition coil ground. Refer to Distributor Ignition (DI) System Check .

• | Spark plugs for proper heat range. Refer to Owners Manual or Section OB.

• | Check distributor vent system for being restricted or open. Refer to Distributor Vent System Check .

Additional Checks

• | Visually (physically) check: Vacuum hoses for splits, kinks, and proper connections and routing as shown on Vehicle Emission Control Information label.

• | Check TCC operation. TCC applying too soon can cause the engine to spark knock. Refer to Transmission Controls.