How Does A Vehicles Fuel Mixture Get Too Lean?


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Robert Wilbur Profile
Robert Wilbur answered
Lean means NOt enough fuel in mixture. This is a sensor issue. The oxygen sensor detects the lean rich status of the exhaust . The computer uses that reading along with the MAP sensor(manifold absolute pressure sensor) to adjust the time the injectors stay open. MAFS(mass air flow sensor) located in the tube between the air filter and the engine also detects the demand for air (if it gets dirty it will not know exactly how much air demand there is) The TPS(throttle position sensor ) keeps track of user demand, and the tachometer lest the car know how fast the engine is turning. The computer has a preset baseline it uses for the first 5 minutes a car is started, after it warms up the engine control is given to the emission computer, where it adjust for performance, economy , and emissions. Thee is a WOT( wide open throttle ) sensor that over rides the emission computer when the car is "floored"

If any of those sensors are bad you will not get good readings,
If the fuel pressure is low the injectors can not mix enough fuel,
If the injectors are plugged they can not mix fuel,
If the Fuel filter is plugged the same problem occours,

So I realize the answer comes a year late but it applies to nearly all makes and models of computer controlled vehicles, give or take a component here and there. There are ohm meter test that can be performed on individual components, but they have to be done with the battery disconnected and the readings are different for each component , for each car. It gets complicated

The local Auto parts store should have a code reader that will help you ( which you must have done to get the lean reading) from there you should have been able to narrow it down. Your cars computer has fuel pressure test and that did not read, it has injector circuit test so that was ruled out,

The Mass air flow sensor or the O2 sensor are all I can think of....But it has been a year...What did you come up with?

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