98 accord coupe V6 sudden excessive gas use

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pritchaw - 28 Dec 2008 04:35 GMT

THis car bought new began getting only 10-12 mpg about six months ago.
Dealer did major tune up. No improvement. Dealer hooked up computer
which shows perfect air fuel mixture. Sent the readout to Honda
engineers in California who had no suggestion. No evidence of leaks,
does not smoke, runs without skipping, seems to have same power as
ever. Dealer gave up, won't do more. Independent shop put in a new
oxygen sensor, no help. Any help?

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jim beam - 28 Dec 2008 05:24 GMT

> THis car bought new began getting only 10-12 mpg about six months ago.
> Dealer did major tune up. No improvement. Dealer hooked up computer
[quoted text clipped - 3 lines]
> Dealer gave up, won't do more. Independent shop put in a new oxygen
> sensor, no help. Any help?

some obvious stuff - make sure the brakes are not binding.

other than that, replace the 10-year old thermostat - ensures it's not too
open and therefore the engine too cool. that confuses the computer into
thinking you're in warm-up and thus excess gas mode. you may want to
check the tw sensor too. hook up a computer reader that gives you live tw
readings, then compare that to an i.r. reading of the head temperature.
sometimes they "drift" and read cooler than actual.

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Tony Hwang - 28 Dec 2008 06:49 GMT

>> THis car bought new began getting only 10-12 mpg about six months ago.
>> Dealer did major tune up. No improvement. Dealer hooked up computer
[quoted text clipped - 12 lines]
> readings, then compare that to an i.r. reading of the head temperature.
> sometimes they "drift" and read cooler than actual.

Hi,
If in warm up mode, idle rpm will be higher than normal.

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jim beam - 28 Dec 2008 07:49 GMT

>>> THis car bought new began getting only 10-12 mpg about six months ago.
>>> Dealer did major tune up. No improvement. Dealer hooked up computer
[quoted text clipped - 14 lines]
> Hi,
> If in warm up mode, idle rpm will be higher than normal.

only if the engine is idling! while driving, the symptom for automatics
is non-switching of the lock-up clutch. i can tell you from personal
experience, the idle can be fine, but the computer refuse to signal
lockup. you don't have that indicator on a stick. hence you need to
check the sensor by comparing what the computer thinks it's seeing and
what temp the head really is.

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slee - 28 Dec 2008 07:48 GMT

Hi,
It is an excellent and strong car. Engine devices are strong. It looks like
Honda. I think that problem arises only using perfect air fuel mixture. Their
gars are not struck in running. Any how repair car immediately and then
observe the working process of the engines.
------------------------------------------
Scott Lee

<a href="http://www.freecarforum.com">New Cars</a>

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Tegger - 28 Dec 2008 14:19 GMT

pritchaw <pritchaw@gmail.com> wrote in news:0504f7f6-7815-411c-a465-
e928529e5b3d@r32g2000vba.googlegroups.com:

> THis car bought new began getting only 10-12 mpg about six months ago.
> Dealer did major tune up. No improvement. Dealer hooked up computer
[quoted text clipped - 3 lines]
> ever. Dealer gave up, won't do more. Independent shop put in a new
> oxygen sensor, no help. Any help?

Did the dealer use the proper HDS device? HDS gives them extensive
information on all engine parameters. If they can't figure this out, you
need a more diligent dealer.

If the air/fuel mix was "perfect", then you wouldn't be having mileage
problems. Not like 10-12mpg, anyway. Were there no error codes stored at
all?

Signature

Tegger

The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/

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