Legacy Sedan 4WD F4-2.2L SOHC (1992)
Engine Control Module: Customer Interest
Fuel - Low Fuel Volatility & Cold Driveability
NUMBER:
02-87-92
DATE:
12-10-92
APPLICABILITY
ALL 1992 LEGACY A/T AND 1992 SVX
SUBJECT:
EFFECTS OF LOW RVP FUEL ON COLD STARTABILITY/DRIVEABILITY
The Clean Air Act of 1990 required that fuel volatility of gasoline sold at retail be reduced at summer months (June through September 15). In 1992, the
EPA implemented Phase II requirement which further lowered the acceptable vapor pressure to 9.0 psi. In some areas, the regulation requires vapor
pressure be no greater than 7.8 psi. Volatility is the term used to describe the fuel's ability to vaporize, or change from a liquid to a vapor. Low volatility
gasoline helps reduce hydrocarbon emissions from evaporated fuel. "RVP" is the abbreviation for "Reid Vapor Pressure", a method used to measure fuel
vapor pressure. This requirement is needed to protect our environment and improve air quality.
The downside of this regulation is its effect on engine cold starting and cold drive away during summer months. This complaint only occurs for a very
short period after start-up and does not severely hamper the driveability. It is important that our customers are aware of the availability of these low RVP
fuels and their effect. The few moments of engine roughness are a small inconvenience when the overall improvement of the atmosphere is considered.
We all have an obligation to improve air quality and we are sure that Subaru customers wish to share in this endeavor to improve our air quality.
Our investigation has proven that there is variation in fuel quality and vapor pressure among retail gasoline supplies. In many cases, the cold start
complaint can be reduced or eliminated by changing fuel brands or stations.
In the interest of customer satisfaction, we have developed a ROM for the ECU of 1992 Legacy automatic transmission and SVX vehicles whose owners
cannot accept the effects of low RVP fuel. Installation of the ROM should only be performed after explanation of the above to the owner and after trying
a different brand of fuel.
This ROM will not totally alleviate the complaint. Also, there is no countermeasure available for manual transmission Legacy or other models. Our
experience shows that these vehicles have few complaints and they can be resolved using a different brand of fuel.
Naturally, you must confirm that the engine is operating properly by basic checks of mechanical and fuel management systems prior to installing the
ROM.
This ROM will also help reduce the occurrence of source detonation or "pinging" on 92MY Legacys.
ROM INSTALLATION PROCEDURES
1.
Remove battery negative terminal.
2.
Hands must be clean and free of dirt and grease prior to handling ROM.
3.
Remove static charge from your body by momentarily touching an earth ground, such as a cold water pipe, metal building support beam or clean
metal area of vehicle.
4.
Remove ECU and its top cover by removing 6 Phillips head screws.
5.
Locate the ROM socket and remove the protective tape.
6.
Align the notch in the new ROM with the notch in the ROM socket. See illustration. It is very important that the notches are located on the same
side to prevent permanent damage to the control unit. Insert the ROM pins into the socket receptacles as follows:
a)
Install the pins on one side of the ROM.
b)
Using a pencil (non-metallic) laid sideways against the unseated pins, press in on the pencil until the pins line up. Make sure all pins are
aligned.
c)
Press down on the ROM to fully seat it into the socket.