ENG.ROUGH/STRAY IGN. PULSE RE-ORIENTING DISTRIBUTOR
MODELS AFFECTED: 1983 Century or Skylark With 2.8L V-6 Engines, RPO, LE2, Or LH7
Some early production 1983 Centurys or Skylarks with 2.8L, LE2, or LH7 engines may exhibit an engine roughness which can be caused by stray electronic signals received by the distributor module which produces a false (high RPM) tach reference pulse to the ECM. The roughness is most evident at idle, but may persist during acceleration and at driving speeds.
Roughness caused by the false reference pulse can be alleviated by re-orienting the distributor module and re-routing the lead wires as follows:
1. Disconnect primary coil leads at the coil.
2. Disconnect the ECM four (4) wire connector.
3. Remove the ignition wires and coil wire from the distributor cap.
4. Remove the distributor cap.
5. Cut a 230mm (9 inch) length of .350 I.D. conduit (Part Number 8919354) and install on the distributor primary leads. Cut an 85mm (3.3 inch) length of the above conduit and install on the four (4) wire ECM leads at the distributor.
6. Crank the engine until the white timing mark on the torsional damper and the "0" on the timing indicator are in alignment and the distributor rotor is in the #1 spark position.
7. Remove the distributor clamp screw and hold down clamp.
8. a. Slowly raise the distributor until the rotor just stops turning counterclockwise.
b. Rotate the distributor base and rotor simultaneously in a clockwise direction until the lead wires are in a 7 o'clock position when viewed along the centerline of the engine from the rear face of the engine. Be sure the distributor is rotated enough so that the lead wires clear the coil bracket hold down bolt.
9. Reinstall the distributor and hold down clamp and clamp screw (loose).
10. Reinstall the distributor cap.
11. Reinstall the ignition wires and coil wire in their original terminal posts. In those applications where #3 ignition wire proves to be too short, substitute ignition wire, Part Number 12036948 (24 inches long).
12. Route the primary coil lead under the right side (wires 1,3,5) ignition wires and attach to the coil.
13. Set the timing to specifications on the tune-up label and tighten the hold down clamp screw.
14. Reconnect the ECM four (4) wire connector.
WARRANTY INFORMATION
LABOR OPERATION NUMBER T0115
LABOR TIME 0.3 HRS.
TROUBLE CODE 92
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.
