Engine - Rough Idle/Hesitation/Backfire/Stalling

91ford16

Article No.
91-8-13

04/17/91


FUEL - USE OF UNLEADED GASOLINES - TIPS TO AVOID LEAN AIR - FUEL CONDITIONS


FORD: 1985-86 LTD
1985-88 EXP
1985-91 CROWN VICTORIA, ESCORT, MUSTANG, TEMPO, THUNDERBIRD
1986-91 TAURUS
1988-91 FESTIVA 1989-91 PROBE

LINCOLN-MERCURY: 1985-87 LYNX
1985-91 CAPRI, CONTINENTAL, COUGAR, GRAND MARQUIS, MARK VII, TOPAZ, TOWN CAR
1986-91 SABLE
1987-91 TRACER

MERKUR: 1985-89 XR4TI
1988-89 SCORPIO

LIGHT TRUCK: 1985-90 BRONCO II
1985-91 AEROSTAR, BRONCO, ECONOLINE, F-150-350 SERIES, RANGER
1989-91 F SUPER DUTY, F47, F53
1991 EXPLORER


ISSUE: Rough idle, hesitation, poor throttle response, induction backfire and stalls during cold start/warm up may be caused by the poor volatility of some high octane premium grade unleaded fuels (91 octane or higher (R+M)/2). When compared to regular grade unleaded fuel (87 octane (R+M)/2), high octane premium grade unleaded fuel may cause long crank time.

ACTION: Use a regular grade unleaded fuel in all vehicles, except where a premium unleaded fuel is recommended in the Owner Guide. If lean air-fuel type symptoms are experienced, determine the grade and brand of fuel used and offer the following service tips.


^ Advise those using a higher octane grade fuel to switch to a regular grade unleaded fuel. For those using a regular grade fuel, advise them to try another brand.

^ Do not advise using a higher octane unleaded fuel than is recommended for that specific engine. Ford engines are designed to perform best using a high quality regular grade unleaded fuel.

^ Only advise using a higher octane unleaded fuel to avoid potentially damaging spark knock or ping, but do so only after mechanical fixes are ineffective.

NOTE: ALL UNLEADED GASOLINES USED SHOULD CONTAIN DETERGENT ADDITIVES THAT ARE ADVERTISED AS HAVING "KEEP CLEAN" OR "CLEAN UP" PERFORMANCE FOR BOTH INTAKE VALVES AND FUEL INJECTORS.

OTHER APPLICABLE ARTICLES: NONE
WARRANTY STATUS: INFORMATION ONLY
OASIS CODES: 404000