ENGINE TICK/KNOCK AT IDLE (REPL. W/SPO GOODWRENCH ENG.)

SUBJECT: ENGINE TICK/KNOCK AT IDLE REPLACE WITH GMSPO (GM SERVICE PARTS OPERATION) GOODWRENCH ENGINE)

MODELS/YEARS: 1993 BRAVADA WITH THE 4.3L (VIN W) ENGINE

CONDITION: Certain 1993 Bravadas with the 4.3L (VIN W) engine may have an idle tick/knock. The noise may occur in park/neutral and/or reverse/drive. The noise is not load sensitive, but may change pitch with engine RPM. The noise may be very intense at 4000 RPM and above. The noise cannot be eliminated by canceling spark to individual cylinders.

CAUSE: Broken camshaft lobe due to incorrect heat treatment. Engines affected will have build dates between September 1, 1992 and October 6,1992.

CORRECTION: Replace engine with GMSPO Goodwrench engine assembly P/N 12520408. Engine assembly replacement is advised due to possible internal damage from camshaft fragments.

PARTS INFORMATION:

Content: Cylinder and case, cylinder head assembly, crankshaft, main and rod bearings, piston and connecting rod assemblies, oil pan and screen assembly, camshaft, valve lifters, push rods, camshaft chain and sprockets, balance shaft, balance shaft drive gears, valve lifter retainer, front cover and pointer, valve rocker cover, oil fill cap, and harmonic balancer.

Additional parts required to dress out a Goodwrench engine: (Quantity: 1 each, except as noted)

Part Description Bravada ---------------- ------- Intake Manifold Gasket Kit 12510908 Knock Sensors 10456082 (Back of engine) 10456146 (Side of engine) Water Pump Gasket (2 required) 03754587 Oil Filter Adapter Gasket 10172754 Oil Filter Adapter Seal 03727474 Bolt-Engine Mounting Bracket (6 required) 09442119

Parts are currently available from GMSPO.

WARRANTY INFORMATION: Use applicable Labor Time Guide.

Note: Applicable miscellaneous items such as engine oil and engine coolant should be added to the above part allowance amount and included in the Net Amount (DMN) column of the claim.

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.