F013/96 DRIVEABILITY CONCERNS
RELATED TO FUEL VOLATILITY
Some driveability concerns are related to fuel volatility. This
bulletin briefly describes some of the symptoms and causes.
- Unleaded gasoline with volatility too high for ambient
temperatures may cause the following concerns during warmed-up driving
and hot restarts:
- Unleaded gasoline with volatility too low for ambient
temperatures may cause the following concerns:
- Long Crank Time
- Rough Idle
- Poor Throttle Response
- Induction Backfire
- 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.
- Verify the concern.
- 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.
- If the concern(s) is still present, the fuel volatility may be
the cause. Refer to the appropriate condition for diagnostic
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
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.
- 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.
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