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

Subject: ENGINE TICK/KNOCK AT IDLE

Model and Year: 1993 M/L VAN AND S/T TRUCKS WITH 4.3L ENGINE

CONDITION:

--------- Certain 1993 M/L vans and S/T trucks with 4.3L (L35) engine (VIN W) 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 cancelling 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 SPO Goodwrench engine assembly part number 12520408. Engine assembly replacement is advised due to possible internal damage from camshaft fragments.

SERVICE PARTS INFORMATION:

GMSPO 4.3L L35 Goodwrench Engine Assembly 12520408

Content: Cylinder and case, cylinder head assembly, crankshaft, main and rod bearings, piston and connecting rod assemblies, T-Truck/L-Van 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 M L S T ----------- ---------------------------------------- Intake Manifold

Gasket Kit 12510908 12510908 12510908 12510908

Knock Sensors 10456146 10456146 10456082 10456082 10456146 10456146 10456146 10456146 Oil Pan (Use old oil pan, if possible) 10054809 Included 10239673 Included

Oil Pump Screen Assembly 03764113 Included 10054774 Included

Water Pump Gasket (2 required) 03754587 03754587 03754587 03754587

Oil Filter Adaptor Gasket 10108436 10108436 10108435 10172754

Oil Filter Adaptor Seal 03727474 03727474 03727474 03727474

Bolt-Engine Mounting Bracket (6 required) 15688341* 15688341* 09442119 09442119

*DO NOT REUSE P/N 15688341. The M/L van requires the use of this bolt to allow the engine assembly to break free of the engine mounts in an extreme frontal collision situation. The bolts are good for ONE installation only!

Parts are currently available from GMSPO.

WARRANTY INFORMATION:

Labor Operation: J 1840*

Replace Engine Assembly ADD TIME:

With Air Conditioning* With Cruise Control* With Automatic Transmission*

*Use applicable Labor Time Guide for labor hours.

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.