EVAP - Hesitation on Light Acceleration

GMC NUMBER: 86-T-148

GROUP: 6E - Engine Emission

DATE: July, 1987


CORPORATE
NUMBER: 636521
SUBJECT: DRIVEABILITY-WARM HESITATION

MODELS: 1982-1986 CABALLEROS WITH 5.0L (VIN CODE H) ENGINES
Some 1982-1986 Caballero models with the 5.0L engine may experience a hesitation on a light acceleration. This hesitation is normally seen after an extended idle or a short hot soak in higher ambient temperatures. This condition could be caused by excessive fuel vapor entering the engine through the canister purge system. To determine if the hesitation is caused by the purge system, the following test should be performed.

1. Vehicle should be at normal operating temperature.
2. On 1982-85 models plug canister purge at Y connector in crankcase vent line. On 1986 models plug canister purge at carburetor.

3. Test Drive Vehicle;

A. Hesitation still present, check for other causes for the hesitation (accelerator pump, timing, etc.).
B. Hesitation no longer present, install fuel vapor canister control kit, P/N 10077501 per instructions in kit.

4. Reconnect purge system.

Labor Operation No: T1200
Labor Time: .5 Hours