Re: My 4.0 is getting REALLY bad gas mileage!
First your mileage needs to be calculated the right way before you can worry about that aspect. Fill the tank and reset the trip odometer. Drive until its just about empty. Refill the tank. Math: Miles driven divided by gallons pumped = MPG. Normal is anywhere between 16-19 depending on driving style and terrain.
Regarding the lean codes, this is usually caused by vacuum leaks, not a faulty MAF. Look for leaking, broken, cracked, or disconnected vacuum lines. The usual culprit is behind the engine under the spark plug wires. This is VERY common and costs a few mere dollars to fix/replace the bad line.
Fuel filter is cheap and easy so you might as well do it. But that isn't going to cause a lean condition.
Last edited by FireRanger; 01-20-2011 at 09:16 PM.
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