Higher octane fuel will make a fuel or spark-related problem worse. It is still gasoline but it is much harder to ignite and burn inside the engine leading to more misfire problems. That characteristic allows engineers to design and TUNE engines to develop more horsepower but the higher octane is needed to prevent spark knock problems. High octane fuel does not produce more power. If there is a problem related to lighting off the fuel and making it burn, the problem will be reduced by using the lowest octane fuel you can find. That will not "fix" a problem, but it will provide a clue.
One thing you can do yourself is to inspect the fresh air tube between the mass air flow sensor and throttle body for cracks or leaks. No air must get into the engine that isn't measured by the mass air flow sensor because the Engine Computer won't command enough fuel to go in with that air.
Your mechanic can measure fuel pressure to be sure it's staying high enough. He will also check for stored diagnostic fault codes related to the problem. Not all codes cause the Check Engine light to turn on. He can also connect a scanner that displays live sensor data and record a few second snapshot of sensor readings when the problem occurs. That data can be reviewed slowly later to see what the various sensors are reporting to the computer.
I would hope there's air in the gas tank. Even when it's "full" there's a few gallons of air to form a crush zone in case of a crash; something lawyers, firemen, and older Ford owners know all about.
That person might have meant air was getting into the fuel supply system. That used to be a problem from a rubber hose in the tank dry rotting and cracking. That could cause sucking up air instead of fuel. The clue was it did not cause a problem when the tank had a certain amount of fuel in it. That was strictly a Ford problem but it occurred on their older cars.
Higher octane fuel will make a fuel or spark-related problem worse. It is still gasoline but it is much harder to ignite and burn inside the engine leading to more misfire problems. That characteristic allows engineers to design and TUNE engines to develop more horsepower without having spark knock problems. High octane fuel does not produce more power. If there is a problem related to lighting off the fuel and making it burn, the problem will be reduced by using the lowest octane fuel you can find. That will not "fix" a problem, but it will provide a clue.
One thing you can do yourself is to inspect the fresh air tube between the mass air flow sensor and throttle body for cracks or leaks. No air must get into the engine that isn't measured by the mass air flow sensor because the Engine Computer won't command enough fuel to go in with that air.
Your mechanic can measure fuel pressure to be sure it's staying high enough. He will also check for stored diagnostic fault codes related to the problem. Not all codes cause the Check Engine light to turn on. He can also connect a scanner that displays live sensor data and record a few second snapshot of sensor readings when the problem occurs. That data can be reviewed slowly later to see what the various sensors are reporting to the computer.
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Tuesday, December 27th, 2011 AT 1:28 AM
