TAILPIPE SMOKE ON START UP DIAGNOSIS INFORMATION

Model and Year: 1987-88 F, Y CARS WITH 5.0L, 5.7L ENGINE 1987-88 C, K, R, V, G, P TRUCKS WITH 5.0L,5.7L ENGINE

This bulletin cancels and supersedes Dealer Service Bulletin 88-383-6, dated December, 1988. New part number and model year applications are provided. All copies of 88-383-6 should be discarded.

Some vehicles may exhibit a puff of tailpipe smoke on startup which is difficult to diagnose. Some hints on diagnosis and recommended corrective action are listed below:

Port Fuel Injection (PFI) Vehicles Only

If the smoke can be characterized as a small puff of black smoke and is accompanied by a longer crank than normal on soaks of several hours, fuel leaking into the engine from the injectors is suspected. Appropriate diagnostic procedures listed in Dealer Service Bulletin 88-382-6E should be followed.

Throttle Body Injection (TBI) and Port Fuel Injection (PFI) Vehicles

If the smoke is white or bluish white, occurs only at startup, and no unusual oil consumption is noted, then the joint between the intake manifold and the cylinder head may be suspect. The intake manifold bolt torques should be checked. The intake manifold bolts (particularly the two bolts nearest each corner) should be removed and the inside of the bolt holes in the manifold should be inspected for signs of threading (grooves cut in the manifold by the bolts). If several of the intake manifold bolts have very low torque (10 ft. lbs. or less) and/or the manifold bolts holes show signs of threading, the intake manifold should be replaced with the appropriate service manifold from the table below.

Engine Intake Manifold P/N ------ ------------------- All (5.0L and 5.7L) TBI 14102183 or 10108448

F-Car (5.0L and 5.7L) PFI 10108516

Y-Car 5.7L PFI 10108517

Parts are expected to be available on April 17, 1989. Until then normal part orders will not be accepted by GMSPO. Only verifiable emergency VIP orders will be accepted. SPO will make every effort to obtain parts. All parts will be placed on 400 control to waive VIP surcharges. However, the part will be shipped premium transportation at dealer's expense. All other order types will be canceled as incorrectly ordered while the 400 control is in place.

If no evidence of manifold threading is found, and the smoke on startup is definitely of a bluish nature or if there is also a comment of oil consumption, the exhaust valve guides should be checked for excessive clearance using the procedure outline in section 6A of the appropriate Service Manual.

Use applicable labor operations and times.

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.