From: Kaz Kylheku on
On 2010-06-30, Tegger <invalid(a)invalid.inv> wrote:
> Kaz Kylheku <kkylheku(a)gmail.com> wrote in
> news:20100629144459.604(a)gmail.com:
>
>> I have a P0170 and P0171 trouble codes.
>
>
>
> Honda does not use P0170. Are you /certain/ the code you see is P0170?
>
>
>
>> The fuel economy is poor (like
>> 9L/100km instead of under 7 where it should be on summer gas),
>
>
> What's that in civilized English?
>
>
>
>> and
>> during warm up, the engine sometimes sputters once or twice. If this
>> happens while idling, the idle RPM suddenly drops very low and the
>> engine runs rough for a few seconds, like it's about to stall (but
>> never does actually stall). If this happens while driving, there is a
>> loss of power: you can floor the pedal, but the car decelerates.
>> Seconds later, there is a sudden surge of power, which literally feels
>> like a kick. This may happen once or twice, and then driveability is
>> just about normal except for a bit of a low idle.
>
>
>
> Makes me suspect EGR, actually...
>
>
>>
>> Running Techron through (a bottle of concentrate into a two thirds
>> full tank) has improved the driveability somewhat, and slightly seems
>> to have mitigated the near-stalling problem. That indicates there
>> maybe had been some buildup which contributes to problems like this.
>>
>> Also, I tried disconnecting the fuel pressure regulator and pinched
>> off the vaccuum hose.
>
>
>
>
> Try pinching the /return hose/, not the vacuum hose.

With the return hose pinched off using a G-clamp, the driving experience
is like this. There is some slight hesitation when accelerating from a
stop during warmup. Acceleration and hill climbing is somewhat poor in
general. The idle is very low, but not rough.

I would say that with the FPR return hose clamped, the car drives
somewhat simlarly to how it drives when the FPR is connected
normally and unrestricted. The best driveability occurs
with the pinched vaccuum line.

But the car is driveable not matter what we do to the regulator; the
fuel pump is clearly working. It may not be a pressure problem at all.

I'm going to do the O2 sensor test described in the service
manual. (Hold engine at 3000 RPM until fan comes on, then
scan the output of #1 O2 sensor, which should be 0.3 to 0.6V.
If it's out of that range, it should be replaced.)

There is also a test described for a stuck or leaking EVAP purge control
valve.
From: Kaz Kylheku on
On 2010-06-30, Kaz Kylheku <kkylheku(a)gmail.com> wrote:
> I'm going to do the O2 sensor test described in the service
> manual. (Hold engine at 3000 RPM until fan comes on, then
> scan the output of #1 O2 sensor, which should be 0.3 to 0.6V.
> If it's out of that range, it should be replaced.)

I did some driving while monitoring the O2 sensors and fuel trim.
Some interesting findings.

The #2 O2 sensor basically has binary behavior it either reads about 0.9xx
volts most of the time except during DFC0 (driving in gear with foot off
throttle), when it reads a low voltage of 0.0xx at 0% fuel trim.

The #1 fuel trim and O2 reading can be described as having demonstrated two
personalities.

During the first fifteen minutes of the run, fuel trim was usually at 46.9%,
when accelerating, driving steadily at around 50-60 km/h, and even when idling
in neutral at stops. The O2 sensor was reading about 0.485 to 0.505 volts all
the time, except when coasting to a stop (DFCO) it would drop down into the
0.2xx range.

Then while I was cruising on a stretch of highway at 90 km/h, the fuel trim
value adjusted down to 35%. The #1 O2 sensor value dropped, to about 0.465.
Next, after I coasted to stop at a red light, the fuel trim cut to 5.5%, and
the O2 reading was only 0.2xx. Big difference from previous stops, when it was
0.4xx and trim at 46%.

After that, there was a bit of street driving at 50-60 km/h before arriving at
my destination. Now, the fuel trim did not go above 35%, and the oxygen sensor
stayed in the 0.3xx range. At each stop, the trim dropped to 5.5% and
the sensor to 0.2xx.

My interpretation is that this may be a bad O2 sensor, since peak value I
observed was 0.505V, even at high fuel trim. It never indicates a rich
mixture. Come on, the car eats a lot of gas, and its exhaust stinks of
unburned fuel. You would think the O2 would indicate rich at some point?

The observed change in behavior could be that the ECU realizes that the O2
lean indication is garbage, and cuts back the rich fuel trim.

Hmm; looks a lot like the repair bucks should be spent in the direction of a
new O2 sensor. Will check for that possible exhaust manifold leak, though.
From: Tegger on
Kaz Kylheku <kkylheku(a)gmail.com> wrote in
news:20100701020701.901(a)gmail.com:


>
> There is also a test described for a stuck or leaking EVAP purge
> control valve.
>



Asking for the THIRD time:
Are you sure you get a P0170 code in addition to the P0171?


--
Tegger
From: Kaz Kylheku on
On 2010-06-30, Tegger <invalid(a)invalid.inv> wrote:
> Asking for the THIRD time:
> Are you sure you get a P0170 code in addition to the P0171?

Yes; I think I can read the screen! Two different OBDII diagnostic programs
show the same two codes. Both codes come back eventually after reset.
From: Tegger on
Kaz Kylheku <kkylheku(a)gmail.com> wrote in
news:20100630135833.210(a)gmail.com:

> On 2010-06-30, Tegger <invalid(a)invalid.inv> wrote:
>> Asking for the THIRD time:
>> Are you sure you get a P0170 code in addition to the P0171?
>
> Yes; I think I can read the screen! Two different OBDII diagnostic
> programs show the same two codes. Both codes come back eventually
> after reset.
>



Honda does not use P0170.

Does your Check Engine light come on for two seconds when you first turn
the key to "II", and then go off and stay off, even after the engine
starts?

--
Tegger