Fuel system too lean code-- last try

I have been getting an intermittent P0171 code, fuel system too lean, along
with a P0170 code, fuel compensation value exceeded the specified range. To
prevent a barrage of useless follow-up questions, here are the specs of my
car: 1998 Honda Accord LX, 4-cylinder, 123k. New spark plugs and
distributor cap.

I don't know where to start to find the source of this problem. If it helps
someone to pinpoint the problem, I have on one or two occasions smelled a
fuel smell while the light was on, and have occasionally had some hesitation
before accelerating from a dead stop (even catching and almost stalling once
or twice). The car also occasionally shakes while driving at a normal
speed.

Thanks for any suggestions about what to do.

 

googling "p0171" got me:

http://autorepair.about.com/library/faqs/bl903d.htm
http://toyotaownersclub.com/forums/index.php?showtopic=9206

mass air flow sensor?

 

id run a couple tanks of fuel cleaner, look into seeing if the mass air
flow sensor is cleanable, reset the code.

do you use gas from a reputable station?

 

Thanks, this is the kind of reply I was hoping for. The fuel that I use is
from either BP or Shell. Ironically, the problem started only AFTER I first
used a fuel injector cleaner a couple months ago.

Does anyone know how to find and clean the Mass Air Flow sensor on a 1998
Honda Accord?

 

afaik, honda don't use air flow mass sensors - they use pressure sensors
& an electronic map of the differential between manifold pressure &
atmosphere for whichever motor it is.

that code is covered in
http://www.alldata.com/TSB/24/982426AX.html
which leads to:
http://www.hondalac.com/service/Bulletins/x00-018e.pdf

replace regulator & vacuum hoses.

 

I could be wrong, but I think you will have a very hard time finding a
mass air flow sensor on that car. Most Honda's use Manifold Absolute
Pressure sensors instead. The MAP sensor is typically located on top of
the throttle body, but I have never heard of a MAP sensor that needs
cleaning.

Some engines us a MAF (mass air flow) sensor to directly measure the
mass air flow, on Honda engines the ECU calculates the mass air flow
based on the output from the Manifold Absolute Pressure sensor, the
Intake Air Temperature sensor and the Throttle Position Sensor.

One possible cause of a "too lean" code is a leak in the exhaust system,
upstream of the oxygen sensor. If you have an exhaust leak, you will
both get exhaust leaking out and fresh air going into the exhaust
system. Fresh air going in will cause the oxygen sensor to sense oxygen
in the exhaust, thus making the ECU believe the mixture is lean.

Another thought is that if the fuel pressure is too low (failed pump or
failed fuel pressure regulator) the injectors may not be able to inject
enough fuel, even if left open for the maximum amount of time available.
This would cause a lean condition as well.

Let us know what you find out!

 

Before I replace vacuum hose and fuel regulator, I need to know if the O2
sensor might be the problem. Does anyone know how to check that? Does a
faulty or "lazy" O2 sensor seem like a possible cause for the system too
lean code?

 

i believe you usually get too rich in that situation. if it were my
car, and there was a t.s.b. for exactly the problem i was experiencing,
i'd be inclined to foillow the t.s.b.'s service procedure /before/
trying to chase anything else.

 

o2 sensors can fail in either direction, lean or rich

 

I did finally end up changing the fuel pressure regulator and rerouting the
vacuum hoses, as suggested in this thread. There was water in the
regulator, causing a lean condition. The repair seems to have solved the
problem.