DRIVEABILITY/PINGING-CORRECT FIX FOR CHUGGLE,HOT SOAK,SURGE

A newly calibrated PROM, P/N 1225948, and EGR valve #17067395, are being released for the correction of any one of or combination of the conditions listed below on California 1981 "A" cars (excluding "A" wagons) with 3.8L V6 engines, when it has been determined that affected systems are within specifications and functioning normally.

A. Chuggle at 40-45 mph B. Hot Soak Surge C. Tip-in Hesitation D. Excess Detonation at 50 mph and higher

Before a decision is made to install both parts, vehicle should be roadtested for the owner described conditions. Unless all other areas are correct, the PROM and EGR valve will not be affective for the purpose intended. Use the attached check lists for additional assistance if necessary.

A. CONDITION: CHUGGLE also referred to as surge, is most noticeable at 40-45 mph and should not be confused with "freeway hop", a common condition in many areas. Converter clutch engage speed is increased to 50 mph from 41 mph.

B. CONDITION: HOT SOAK SURGE may occur at various times, but most noticeable after extended highway driving during hot weather, followed by a parked period of 20 minutes or more. vehicle restart is good, but surge begins shortly after moving off and continues for about 1/4 to 1/2 mile.

C. CONDITION: DETONATION also called "ping" at moderate to heavy acceleration at vehicle speeds of 50 mph and higher.

D. CONDITION: TIP-IN HESITATION may be experienced during either hot or cold operation while going through a light or moderate acceleration period from a stationary vehicle position.

If any one or combination of conditions exists, install both parts, PROM and EGR valve. In addition, complete the following carburetor checks and any necessary corrections.

CARBURETOR CHECKS AND SPECIFICATIONS

Float Level - 11/32" - 12/32". Use gage J-9789-130, BT-7720 or equivalent to make external check. If adjustment required, set to 11/32".

Lean Mixture Screw - 3 1/2 - 3 3/4 turns out. If adjustment required, set to 3 1/2 turns.

M/C Solenoid Plunger Travel (Rod Travel) 4/32" - 5/32". If adjustment required, set to 4/32".

After carburetor is set as listed above, check dwell readings:

Idle, in drive (Canister Purge Hose Disconnected and Plugged at Canister) - 35 DEG to 45 DEG

At 3,000 rpm, in park - 25 DEG to 45 DEG

Should idle dwell require correction, adjust by turning idle air bleed screw. Do not exceed two (2) turns out on air bleed screws when increas- ing idle dwell readings. If necessary, make final idle adjustment by turning rich stop screw down 1/4 to 1/2 turn.

PARTS INFORMATION

Obtain the following two (2) parts from your normal GM Parts Division warehouse:

PROM - 1225948 EGR Valve - 17067395

Both parts must be installed to make the correction effective. DO NOT INSTALL ONE WITHOUT THE OTHER.

WARRANTY INFORMATION

Labor Operation Number - T0061

Labor Times:

Replace PROM and EGR valve .6

- Add for float level check - external method (with air cleaner removed). .1

If float level/carburetor checks indicate the need for adjustment, add for float, lean screw, rod travel, air bleed screw adjustments 1.3 hours.

CHUGGLE CHECK LIST

Park-Neutral Back Up Light Switch Adjustment Base Ignition Timing and Total Advance Spark Plugs and Plug Wires HEI Operation at Problem Speeds - Includes checking for correct Distributor Wave Washer Speedometer Needle for Fluctuation (Sticking or Kinked Cable and/or Speedo Head will Cause Vehicle Speed Sensor (VSS) to Engage - Disengage TCC) Evaporative Emission Control System (EECS) - Purge Solenoid Operation - Hoses and Correct Hose Connections - Canister Vent Valve Operation

HOT SOAK SURGE CHECK LIST

Base Ignition Timing Fuel Line Proximity to Hot Engine Components EGR Valve Operation Vacuum Hoses and Connections Vapor Canister Vent Valve Operation Carburetor Float Level Fuel Pump Pressure

DETONATION CHECK LIST

Ignition Timing EGR Valve System Operation Vacuum Hoses and/or Connection Leaks Carburetor for Lean Operation Deposits in Combustion Chambers Intake Valve Seals not Sealing MAP/BARO Sensor Operation E.F.E. Operation T.A.C. Operation Overheating - Cooling System Problem Incorrect Spark Plugs Bad Fuel EGR Override Relay Circuit

HESITATION CHECK LIST

EGR Valve System Operation Accelerator Pump System Operation - Includes checking discharge check ball seating Vacuum Hoses, Fittings and Connections Ignition Timing Carburetor Float Level C-3 Wiring Proximity to High Voltage Wiring E.F.E. System Operation T.A.C. System Operation

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.