99 Accord - PO171 code

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Our 99 Accord V6 with 168K miles has recently started acting up. CEL
lights up for a day or two, then turns off. Every time the code has been
pulled/reset, it is showing a PO171 (fuel mixture too lean). This is
accompanied by the engine feeling lower on power and not running as
smoothly as usual. When it first started happening about a month ago,
the power loss was much more pronounced - it would suddenly start
stumbling and missing, accompanied by the car decelerating, then just
when I thought it was going to die, it would recover. This would happen
several times during the course of an average trip.

Took it to the local independent shop that I've been using for years.  
They are very familiar with the car and have serviced it since we bought
it (I have also had it serviced at the dealer as well, depending on the
job). They had replaced the front O2 sensor a little over a year ago
when the same symptoms had occurred and the same code was showing up,
and we hadn't had any more problems until now. They could not duplicate
the problem consistently, and said that PO171 was a code that did not
have a single clear-cut cause. IIRC, they also said that this code was
triggered when the fuel trim was above 1.19%; when they measured it was
at .82%.

Before starting to replace parts, they recommended trying a less costly
approach first, starting with running bottles of one of the Techron-
based injector cleaners through the next three full tanks of fuel and
then reassessing. We did that, and although it seems to have slightly
reduced the severity of the problem, it has not gone away.

I've seen all of the following possibilities mentioned online as causing
a PO171 code:

- Front O2 sensor (as mentioned, already replaced a year ago)
- Poor quality or E85 fuel (we had been occasionally filling up at Sam's
Club, but quit doing so after they started selling E85 exclusively)
- Vacuum leak
- Fuel filter (in the fuel tank and not intended to be replaced)
- Fuel pressure regulator
- Fuel injectors (expensive and probably unlikely - the shop said they
could not recall the last time they had to replace OEM Honda injectors)

Anyone else had any experience with this code? Any place else we should
be looking for a cause? I'm inclined to have them go ahead and replace
the fuel pressure regulator next as that seems to be mentioned fairly
frequently as the next most likely suspect after the front O2 sensor.

Also, does anyone still have access to the Honda TechInfo site? I found
a URL to a tech bulletin that is supposed to cover the PO171 code but
it's no longer accessible without an account:



Re: 99 Accord - PO171 code

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Did you try Googling a bit? (Sorry about the long link, if you can't get
it to load, put "99 honda accord p0171" sans quotes in the search bar.):


Also, check this E85 statement from Hondas's website:

http://automobiles.honda.com/information/frequently-asked-questions.aspx ?


Re: 99 Accord - PO171 code
snipped-for-privacy@this.com says...

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get Yes, but not that exact search string - tried several other variations
previously. I've seen a couple of the results from your link but there
were some others I hadn't seen before, and I was able to locate what
looks like the service bulletin I mentioned as well as a related Service
News issue:


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See my previous post - had a brain fart and typed E85 when I meant E15.


Re: 99 Accord - PO171 code
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Sam's Yes, of course. I meant E15, not E85. Neither one goes in either of our

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