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From: Kaz Kylheku on 29 Jun 2010 18:19
I have a P0170 and P0171 trouble codes. The fuel economy is poor (like 9L/100km
instead of under 7 where it should be on summer gas), 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.

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. There is almost no difference, though I'd swear there is a bit
more power at the lower RPMs. When accelerating normally in second gear,
it seems more eager. Also, there is usually a certain little ``power notch''
somewhere above 2000 RPM which doesn't seem to be there when the FP is cut off
from vaccuum. The near-stall on warmup still occurs, though.

I don't currently have a fuel pressure gauge to be able to investigate
pressures.

But is there enough evidence that it may be purely a mechanical fuel pressure
problem, (rather than, say, faulty O2 sensor readings?)

Is there anything I can diagnose with OBDII before I shop for a fuel pressure
gauge?

I haven't found any loose vaccuum hoses around the intake manifold.

I don't think I have an exhaust manifold leak, either. I had one previously
which was so bad, you could smell it from the ventillation; and there was no
such code coming up. The driveability was way worse than now. I recently,
about two months ago, changed the top O2 sensor (for a working used one, which
came from my old broken manifold), at which time I inspected the exhaust for
cracks; didn't see any at that time.
From: Tegger on 29 Jun 2010 23:00
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.




There is almost no difference, though I'd swear
> there is a bit more power at the lower RPMs. When accelerating
> normally in second gear, it seems more eager. Also, there is usually
> a certain little ``power notch'' somewhere above 2000 RPM which
> doesn't seem to be there when the FP is cut off from vaccuum. The
> near-stall on warmup still occurs, though.
>
> I don't currently have a fuel pressure gauge to be able to investigate
> pressures.
>
> But is there enough evidence that it may be purely a mechanical fuel
> pressure problem, (rather than, say, faulty O2 sensor readings?)
>
> Is there anything I can diagnose with OBDII before I shop for a fuel
> pressure gauge?



The manual lists a whole bunch of possible causes of P0171. I'm not sure
you can do this one yourself without shotgunning lots of uselessly-spent
money at the car.




--
Tegger
From: Scott Dorsey on 29 Jun 2010 23:02
Kaz Kylheku <kkylheku(a)gmail.com> wrote:
>I don't currently have a fuel pressure gauge to be able to investigate
>pressures.
>
>But is there enough evidence that it may be purely a mechanical fuel pressure
>problem, (rather than, say, faulty O2 sensor readings?)
>
>Is there anything I can diagnose with OBDII before I shop for a fuel pressure
>gauge?

When did you last change your fuel filter?

>I don't think I have an exhaust manifold leak, either. I had one previously
>which was so bad, you could smell it from the ventillation; and there was no
>such code coming up. The driveability was way worse than now. I recently,
>about two months ago, changed the top O2 sensor (for a working used one, which
>came from my old broken manifold), at which time I inspected the exhaust for
>cracks; didn't see any at that time.

I'd still get out a propane torch and make a basic test for leaks.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
From: Kaz Kylheku on 30 Jun 2010 01:10
On 2010-06-30, Scott Dorsey <kludge(a)panix.com> wrote:
> Kaz Kylheku <kkylheku(a)gmail.com> wrote:
>>I don't currently have a fuel pressure gauge to be able to investigate
>>pressures.
>>
>>But is there enough evidence that it may be purely a mechanical fuel pressure
>>problem, (rather than, say, faulty O2 sensor readings?)
>>
>>Is there anything I can diagnose with OBDII before I shop for a fuel pressure
>>gauge?
>
> When did you last change your fuel filter?

Never. The service table doesn't mention the fuel filter at all. Though
it does seem odd that thousand and thousands of liters of fuel can pass
through this little thing, and yet no change interval is published.

I've already looked up the change procedure, and how much the
new filter costs from a couple of sources.
From: Tegger on 30 Jun 2010 08:00
Kaz Kylheku <kkylheku(a)gmail.com> wrote in
news:20100630140244.128(a)gmail.com:

> On 2010-06-30, Scott Dorsey <kludge(a)panix.com> wrote:
>> Kaz Kylheku <kkylheku(a)gmail.com> wrote:
>>>I don't currently have a fuel pressure gauge to be able to
>>>investigate pressures.
>>>
>>>But is there enough evidence that it may be purely a mechanical fuel
>>>pressure problem, (rather than, say, faulty O2 sensor readings?)
>>>
>>>Is there anything I can diagnose with OBDII before I shop for a fuel
>>>pressure gauge?
>>
>> When did you last change your fuel filter?
>
> Never. The service table doesn't mention the fuel filter at all.



It's very unlikely the fuel filter is the cause of this problem.


> Though it does seem odd that thousand and thousands of liters of fuel
> can pass through this little thing, and yet no change interval is
> published.
>
> I've already looked up the change procedure, and how much the
> new filter costs from a couple of sources.



Have you checked to make certain you're actually getting a P0170? If you
are, there's another possible cause that's not mentioned in the manual.

--
Tegger
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