ENGINE SURGE OR MISFIRE RELOCATE IGNITION COIL

VEHICLES AFFECTED: 1987 "F" CARS WITH 5.0L LB9 PFI ENGINES (VIN CODE F)

Engine surge or engine misfire 'may occur on some 1987 'F' cars with LB9 PFI engines. This condition is most evident between 1700 and 2100 RPM at steady throttle conditions. This condition may also be accompanied by a variation or fluctuation in the engine tachometer reading.

This condition is caused by electromagnetic interference (EMI) - false reference signals are generated due to the ignition coil being mounted too close to the distribkltor. These false reference signals cause the ignition coil to discharge at inappropriate times, resulting in the engine misfire.

This condition can be repaired by moving the ignition coil away from the distributor: The procedure required is as follows:

1. Reverse the present ignition coil mounting position by 180 degrees so that the secondary side of the coil is located outboard of the distributor.

2. Reroute the primary ignition coil wire (pink/white pigtail) around the back of the distributor to the coil.

3. Use secondary ignition coil wire, P/N 12053452, it is slightly longer than the current wire, and the extra length is necessary.

4. Reroute #2 spark plug wire so that it runs between posts #4 and #8 an top of the distributor cap. All spark plug wires, including #6 should then be routed forward of the ignition coil.

5. Reposition right hand side Rocker Cover Engine Wiring Harness between the ignition coil and the distributor.

6. Reposition right hand side ECM Harness (to fuel injectors) between the rocker cover and the coil mounting bracket.

7. Make sure the inlet heater hose is routed between the coil in its new position and the transmission fill tube on automatics.

Warranty Information

Use the most applicable labour operation from the Canadian Labour Time Guide and claim 0.4 hours.

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.