COLD DRIVEABILITY EFE-POOR LOW TEMP. PERFORMANCE

1984 1500-3500 C, K, G, P MODELS WITH 5.0L AND 5.7L V8

This bulletin cancels and supersedes 84-B-98 (August 1984), all copies of which should be destroyed. This copy identifies additional vehicle applications.

1984 Model Engine Emission System Engine Code ---------- ------- ---------------- ------------ Pickup, Vandura, Suburban, and Jimmy 5.0L V8 Federal/California H

Pickup, Vandura, Suburban, Jimmy, and Hi-Cube Van 5.7LV8 California M

Pickup, Suburban, and Motor Home 7.4LV8 California W

Some 1984 trucks, as listed above, may exhibit poor driveaway and perform- ance when cold. When diagnosing cold driveability and performance conditions refer to the Shop Manual Driveability and Emissions Diagnosis Section. If the condition cannot be resolved by normal diagnostic procedures, check the EFE (Early Fuel Evaporation) valve for proper operation (Chart C-9C).

After starting the cold engine, observe the EFE valve. If the EFE valve does not close, follow the diagnostic procedure shown on chart C-9C. If the condition is not corrected, the following procedure should be performed.

1. Remove the check valve from the vacuum supply line as shown.

2. Reconnect the vacuum supply line by inserting a straight hose connector, P/N 560625.

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.