Lean codes and looses power

[GlenB]

Everything... pretty much... that is needed to determine what is wrong with this vehicle is shown in the 2 screen captures. Would anyone like to take a crack at what is wrong? Or any questions about what is going on in the data capture?

For what is is worth, this is a 2006 Explorer. But that only matters for the specifics. The general principle here applies to any make.

[GlenB]

Ok, the vehicle in question is an 06 Explorer, but for the basic principles here, it really doesn't matter what kind of car this is.

Some of the fault codes found are "lean". In the world of automotive, to be "lean" means that the engine is not getting enough fuel in the eyes of the PCM.

The symptoms here were normal power from idle and up to mid power demand by the driver... so as long as the driver was a little old man, he may not have complained about it... it would have felt good.

But, as soon as the driver would want to pass someone, the vehicle would go from normal power to just fall on it's face.

Here is what is happening in the data captures. The lower window shows to pieces of information. The red trace is how much throttle I'm trying to give it and the blue trace is how much strain (load) the engine is under.

In the upper window, the red trace is how much fuel pressure the PCM is trying to make happen out of the pump (in a round about way... but that is what is boils down to), and the red trace is how much fuel pressure is actually occurring.

At the 91 second mark (time scale across bottom) you can see in the lower window that I opened the throttle wide open (red trace climbed up). After a couple of seconds at being at wide open throttle, the fuel pressure fell down to around 6psi. That is seen in blue trace in the upper window. The PCM wanted more pressure as can be seen in the red trace at the upper window... but the pump just couldn't do it. When I let off of the gas pedal, around the 150 second mark... the pressure came back up because the pump could keep up with that much demand.

So, loss of power on hard acceleration and lean codes.... it was due to a bad fuel pump. A stopped up fuel filter or a kink in the fuel line could have done the same thing.

99% of diagnosing this problem was done from the driver's seat and through the DLC connector under the dash.