"herdboy24" <aherdfom@hotmail.com> wrote in
news:1169582308.766632.280490@k78g2000cwa.googlegr oups.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 site
http://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 FAQ
www.tegger.com/hondafaq/