Tegger, excellent reply! Looking over the list, most of these items
would generate a code that would also show with an OBDII reader. So,
let's assume the person who gave this guy the P0171 knew what he was
doing and that was the only code. Just curious though... has this
owner ever replaced the gas cap, like, leaving the original at a gas
pump somewhere and picking one up aftermarket? Some caps are vented,
others aren't and the wrong one on the 2002 Civic will do weird stuff.
Perhaps an easy fix!

On Jan 23, 6:01 pm, Tegger <teg...@tegger.c0m> wrote:
> "herdboy24" <aherd...@hotmail.com> wrote innews:1169582308.766632.280490@k78g2000cwa.google groups.com:
>
>
>
>
>
> > I have a 2002 Honda Civic EX. I am having trouble with the
> > cars gas mileage and also with power. Here is what its doing: Every
> > time I get to a ¼ of a tank it runs really bad. At first when I am
> > starting my car it has to crank like 4 or 5 times before it will fire
> > up but if I crank it once or twice and then turn it to the off
> > position and then try again it will fire right up like it is suppose
> > to. The other things it is doing is it will stall out on me when I try
> > to accelerate and sometimes will die unless I ride the clutch. Then
> > when I am just sitting at an intersection it will stutter and bog out
> > like it wants to die. The catch to it is though when I am on a full
> > tank it runs fine except for the bad gas mileage. I am not a mechanic
> > by any means and I have taken this car to 3 different people and have
> > gotten 3 different answers. I am tired of wasting my money with
> > dishonest people.
> > The check engine light is on and it reads P0171 System Too
> > Lean (bank 1), but why would I be getting this bad of gas mileage.This _is_ curious, so I did a bit of digging of my own.
>
> It seems the term "system too lean" paradoxically means you are
> running RICH.
>
> In short, the ECM is being told by the oxygen sensor that
> the mixture is too lean, and it therefore attempts to enrich the mixture
> through the use of "fuel trim", right up to its limit of adjustment.
>
> But since the ECM never ends up being told the mixture has been
> corrected, and having reached the limits of its "fuel trim" range
> without obtaining the proper report from the oxygen sensor, it reasons
> the system is still too lean and sets the P0171.
>
> The question then arises: Why is the ECM being told the system is too
> lean? There is no short answer. From this Toyota sitehttp://www.4x4wire.com/toyota/4Runner/tech/OBDII_ECU/comes this list of
> potential culprits:
> * Air Induction System Leak
> * Injector Blockage
> * Mass Air Flow Meter
> * Engine Coolant Temperature Sensor
> * Fuel Pressure
> * Gas Leakage from the Exhaust System
> * Open or Short in the Oxygen Sensor or associated wiring
> * Oxygen Sensor Defective
> * Engine Control Unit
>
> You need to have a competent dealer tech sort this out. I'd guess about
> $100 for diagnosis.
>
> --
> Tegger
>
> The Unofficial Honda/Acura FAQwww.tegger.com/hondafaq/- Hide quoted text -- Show quoted text -