F013/96 DRIVEABILITY CONCERNS RELATED TO FUEL VOLATILITY

APPLICABLE MODELS

All Models

DESCRIPTION

Some driveability concerns are related to fuel volatility. This bulletin briefly describes some of the symptoms and causes.

SYMPTOM

1. Unleaded gasoline with volatility too high for ambient temperatures may cause the following concerns during warmed-up driving and hot restarts:
   • No Start
   • Rough Idle
   • Surging
   • Vapor Lock

     NOTE: These symptoms are most typical during spring and summer months when winter gasoline may still be available.

2. Unleaded gasoline with volatility too low for ambient temperatures may cause the following concerns:
   • Long Crank Time
   • Rough Idle
   • Hesitation
   • Poor Throttle Response
   • Induction Backfire
   • Stalls
   • Similar symptoms caused by lean operation during initial cold starts and drive-away.

NOTE: Gasoline's volatility is higher (vaporizes easily) in the winter and lower in the summer.

REPAIR PROCEDURE

1. Verify the concern.

2. Perform the diagnostics in section F of the workshop manual .

   NOTE: Often, no trouble codes are found if the concern(s) are caused by gasoline.

3. If the concern(s) is still present, the fuel volatility may be the cause. Refer to the appropriate condition for diagnostic information.

WARM ENGINE - WARM / HOT AMBIENT TEMPERATURES

• Recommend that the customer try to identify a source of fresh, good quality gasoline. A station which receives frequent shipments of fuel will likely be a source of fresh, good quality gasoline.
• Using such gasoline may be more appropriate for these ambient temperatures.

COLD ENGINE - COLD AMBIENT TEMPERATURES

• Advise customers using a higher than recommended octane to switch to the recommendations in the owner's manual.
• Do not advise using a higher octane than recommended for that engine. Premium octane grade unleaded gasoline does not provide better fuel economy or performance than regular octane grade gasoline. Only advise using a higher octane grade gasoline to avoid potentially damaging "spark knock" or "ping." Recommend this octane only after diagnostic procedures are ineffective.
• Advise customers using the recommended octane grade unleaded gasoline to try another brand.
• If customers are using a gasoline containing an oxygenate, advise them to try another brand of oxygenated gasoline. If possible, advise customers in this category to try a gasoline which is not oxygenated.

NOTE: The oxygenate type should be posted on the pumps.

GENERAL INFORMATION

• No fuel additives will resolve this concern(s).
• Always use a gasoline with a "In-tank System Deposit Control" detergent that helps maintain proper operation of fuel injectors and keeps valves clean.
• This information may be used on any model year vehicles exhibiting these concerns.