KNOCK / PING Perpetrators
Fuel Quality as MS88Bronc advised
Base Timing as MS88Bronc advised.
See my Vacuum leak test in post #11 incl jowens126 HVAC Control Panel info & Mikey350 HIGH IDLE
tests @ Help with dtc codes and idle
When vacuum leaks are indicated, search out and correct the condition. Excess air leaking into the system will upset the fuel mixture and cause conditions such as rough idle, missing on acceleration, or burned valves. If the leak exists in an accessory unit, such as the power brake, the unit will not function correctly. Or Air Conditioning when in MAX mode may switch to Defrost
FUEL - VOLATILITY RELATED DRIVEABILITY INFORMATION
FUEL - INFORMATION ON GASOLINE - TIPS TO
RESOLVE VOLATILITY RELATED DRIVEABILITY
1992-96 CROWN VICTORIA, ESCORT, MUSTANG, PROBE, TAURUS, THUNDERBIRD
1992-94 CAPRI, TOPAZ
1992-96 CONTINENTAL, COUGAR, GRAND MARQUIS, SABLE, TOWN CAR, TRACER
1993-96 MARK VIII
1992-96 AEROSTAR, BRONCO
, ECONOLINE, EXPLORER, F-150-350 SERIES, F-47, RANGER
This TSB article is being republished in its entirety to include 1995-96 model year vehicles.
Additional information on gasoline tips to resolve volatility related driveability concerns have been developed.
Refer to the following text for further information.
WARM ENGINE/WARM-HOT AMBIENT TEMPERATURE DRIVEABILITY CONCERN
Unleaded gasoline with volatility too HIGH for ambient temperatures cause hot-start/warmed-up driveability concerns such as no start, rough idle, surging and other "vapor lock" related concerns during warmed-up driving and hot engine restarts.
COLD ENGINE/COOL AMBIENT TEMPERATURE DRIVEABILITY CONCERN
Unleaded gasoline with volatility too LOW for ambient temperatures cause cold-start/warm-up driveability concerns such as long crank times, rough idle, hesitation, poor throttle response, induction backfire, stalls and similar symptoms caused by lean operation during initial cold start and driveaway.
Gasoline distribution practices often do not allow branded marketers to have much control over their gasoline's volatility other than Reid Vapor Pressure (RVP). Oxygenate (e.g., ethanol, methyl tertiary butyl ether (MTBE)) use is more dependent on local gasoline markets, rather than specific marketers practice. Therefore, it is difficult to recommend specific brands to avoid volatility related complaints.
Gasolines are seasonally adjusted, meaning they have higher volatility (vaporize easier) in the winter and lower volatility in the summer. Recent government mandates to improve air quality have caused significant changes to gasolines, such as the mandatory use of oxygenates (ethanol, MTBE and others), in the winter or the reduction of RVP in the summer. The addition of oxygenates (especially ethanol) increases volatility while the reduction of RVP reduces volatility.
RVP is one measure of volatility, and probably the most familiar, but RVP alone does not sufficiently characterize the volatility of the gasoline. As a gasoline is a complex blend of hydrocarbon (and oxygenate) liquids, it has a boiling range rather than a single boiling temperature (like water). The concerns are largely caused by the characteristics of this boiling range, called the distillation curve.
Unfortunately, fuel vapor pressure measured with the Rotunda Gas Check 014-00335, and similar tools, does not sufficiently analyze the gasoline distillation curve. The gas check tool may be used to determine alcohol and water content, although a gasoline that tests satisfactorily with these tools may still cause driveability concerns due to the distillation curve which cannot be measured by these tools. Currently, no service tools are available to measure the distillation curve.
Often no trouble codes will be found. If the subject concerns are not corrected through engine/emission diagnostic routines, the concerns may be caused by the gasoline. The following tips may help further diagnose these concerns.
WARM ENGINE/WARM-HOT AMBIENT TEMPERATURE DRIVEABILITY CONCERNS
Typically experienced during periods of unseasonably warm weather during the spring or early summer when winter gasolines are still available.
Through experience, try to identify a reliable source for fresh, good quality gasoline such as a station that receives frequent shipments. Using such gasoline should be more appropriate for ambient conditions and should resolve the concern.
No fuel tank additives will resolve these concerns.
COLD ENGINE/COOL AMBIENT TEMPERATURE DRIVEABILITY CONCERNS
Some Premium Octane Grade gasolines (91 (R+M)O/2 or higher) in the past have caused this concern, however during the past two summers these concerns have also been caused by some Regular Octane Grade gasolines. As RVP was lowered (summer 1992) to meet EPA mandates, the distillation characteristics of the gasoline that influence cold start/warm-up performance were not adjusted to compensate for the lower RVP. These characteristics were allowed to become similar to the premium gasolines that had caused concerns in the past.
^ Advise customers using a higher octane grade than recommended in their Owner's Guide to switch to the recommended grade (for most vehicles regular octane grade unleaded gasoline 87 (R+M)/2).
^ DO NOT advise using a higher octane grade unleaded gasoline than is recommended for that specific engine. Premium octane grade unleaded gasolines do not provide better fuel economy or performance than regular octane gasolines. Only advise using higher octane grade unleaded gasoline to avoid potentially damaging spark knock or ping, but do so ONLY after diagnostic procedures have been ineffective.
^ Advise customers using the recommended octane grade unleaded gasoline to try another brand.
^ Advise customers using a gasoline containing an oxygenate to try another type of oxygenated gasoline, or if available, a gasoline that does not contain an oxygenate. The oxygenate type, and perhaps the amount, should be posted on the pumps.
^ No fuel tank additives will resolve these concerns.
ALWAYS USE AN UNLEADED GASOLINE WITH AN "INTAKE SYSTEM DEPOSIT CONTROL" DETERGENT THAT HELPS MAINTAIN PROPER OPERATION OF YOUR VEHICLE'S FUEL INJECTORS, AS WELL AS KEEPING THE VALVES CLEAN.
●THESE TIPS MAY BE USED ON ANY MODEL YEAR VEHICLE EXHIBITING THESE CONCERNS.
OTHER APPLICABLE ARTICLES: 91-8-13
WARRANTY STATUS: INFORMATION ONLY
OASIS CODES: 40200, 404000, 602300, 603300, 607000, 607400, 608000, 608400, 609000, 609400, 610000, 611000, 611500, 612000, 614000, 614500, 623000