TAILPIPE SMOKE ON START-UP DIAGNOSIS INFORMATION

SUBJECT: TAILPIPE SMOKE ON STARTUP (DIAGNOSIS)

VEHICLES AFFECTED: 1987-89 B/F AND Y CARS W/5.0L AND 5.7L

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:

ALL V-8 ENGINES - (1987-89 MODEL YEAR)

If the smoke is blue or bluish white and occurs only at startup, the recommended corrective action should be installing valve seal kit P/N #10132715. This kit incorporates an umbrella seal for the exhaust valve stem and should be installed. See Section 6A4 of applicable Shop Manual for assembly sequence.

PORT FUEL INJECTION (PFI) VEHICLES ONLY - (1987-88 MODEL YEARS 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.

THROTTLE BODY INJECTION (TBI) AND PORT FUEL INJECTION (PFI) VEHICLES (1987-88 MODEL YEARS ONLY)

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 14 Km (10 ft. lbs.) or less and/or manifold bolt holes shown signs of threading, the intake manifold should be replaced with the appropriate service manifold from the table shown.

ENGINE INTAKE MANIFOLD P/N

All (5.OL and 5.7L) TBI 14102183 (10108448 optional)

F-Car (5.OL and 5.7L) PFI 10108516

Y-Car 5.7L PFI 10108517

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.