97 4 Cylinder Camry with DTC P0171

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Old 22 Jul 2003, 12:04 pm   #1 (permalink)
marvin shostack
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Default 97 4 Cylinder Camry with DTC P0171

Please help.

My Check Engine Light has come on and I have determined that it was
caused by Diagnostic Trouble Code P0171, System too Lean. There are no
other codes and the car behaves normally in every respect.

I don't believe I have a vacuum leak as the idle speed is correct.

I don't believe the problem is low fuel pressure as the car has normal
acceleration and does not bog.

My theory is that I have a lazy Air/Fuel sensor (not called O2 sensor
for California emissions). It seems to me that the only feedback the
emissions control computer has that would cause a lean trouble code is
the Air Fuel sensor.

There is one more piece of information, the Fuel Trim indication was
-11%. I am hoping that I can get some technical advice before I spend
$240 on a replacement Air/Fuel sensor.

Thanks in advance.

Marvin
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Old 22 Jul 2003, 04:08 pm   #2 (permalink)
Jason James
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Default Re: 97 4 Cylinder Camry with DTC P0171


"marvin shostack" <marvinshos@yahoo.com> wrote in message > My theory is
that I have a lazy Air/Fuel sensor (not called O2 sensor
> for California emissions). It seems to me that the only feedback the
> emissions control computer has that would cause a lean trouble code is
> the Air Fuel sensor.
>
> There is one more piece of information, the Fuel Trim indication was
> -11%. I am hoping that I can get some technical advice before I spend
> $240 on a replacement Air/Fuel sensor.
>
> Thanks in advance.
>
> Marvin


Marvin, before you spend that amount of money, get your vehicle's exhaust
checked on an Exhaust gas analyser. This device (and they have been around
since Adam was a boy) will tell you accurately if your engine is running the
wrong mixture and what air/fuel ratio it is. You can even take it onboard
(they are battery operated) and test the car on the road (the
rubber/neoprene hose is attached to the exhaust tip with a clamp).

Any engine analyser rig from the last 30 yrs has one, so go to any mechanic
who uses one.

Jason


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Old 22 Jul 2003, 07:21 pm   #3 (permalink)
Mark Uhlenkamp
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Default Re: 97 4 Cylinder Camry with DTC P0171

P0171 is most likly caused by a dirty or faulty Mass Air Flows Sensor. Dirty
MAF Sensors are often caused by over oiled K&N air filters.
MU



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Old 22 Jul 2003, 08:35 pm   #4 (permalink)
grimm@nospam.com
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Default Re: 97 4 Cylinder Camry with DTC P0171

I had the same problem on my 98 4 cylinder last year. I replaced the
spark plugs, and air filter... then finally took it to the dealer, they
determined it was the air fuel sensor. they replaced it and then about 3
months later the light came back on... brought it back to them told them
that it was replaced few months ago... tech did a test on it and said the
sensor was dirty... they replaced it for free since it was under the
warranty... so i got 2 sensors for the price of one... paid $431...
what a rip.... $279 for the sensor, and 2 hours labor...

btw, had two codes present P0171 System too lean (fuel trim) and P1133,
AF sensor circuit slow response malfunction (bank 1, sensor 1)


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Old 22 Jul 2003, 10:53 pm   #5 (permalink)
MB
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Default Re: 97 4 Cylinder Camry with DTC P0171

Check the Mass A/F sensor as others suggested, but before you shell out
240 plus for the Toyota heated O2 sensor, Bosch makes one for about 69
bucks that will work. AutoZone has 'em.

mike
-------------------------

marvin shostack wrote:
>
> Please help.
>
> My Check Engine Light has come on and I have determined that it was
> caused by Diagnostic Trouble Code P0171, System too Lean. There are no
> other codes and the car behaves normally in every respect.
>
> I don't believe I have a vacuum leak as the idle speed is correct.
>
> I don't believe the problem is low fuel pressure as the car has normal
> acceleration and does not bog.
>
> My theory is that I have a lazy Air/Fuel sensor (not called O2 sensor
> for California emissions). It seems to me that the only feedback the
> emissions control computer has that would cause a lean trouble code is
> the Air Fuel sensor.
>
> There is one more piece of information, the Fuel Trim indication was
> -11%. I am hoping that I can get some technical advice before I spend
> $240 on a replacement Air/Fuel sensor.
>
> Thanks in advance.
>
> Marvin

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Old 22 Jul 2003, 10:56 pm   #6 (permalink)
Jason James
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Default Re: 97 4 Cylinder Camry with DTC P0171


<grimm@nospam.com> wrote in message news:3F1DE668.2904A05C@nospam.com...
> I had the same problem on my 98 4 cylinder last year. I replaced the
> spark plugs, and air filter... then finally took it to the dealer, they
> determined it was the air fuel sensor. they replaced it and then about 3
> months later the light came back on... brought it back to them told them
> that it was replaced few months ago... tech did a test on it and said the
> sensor was dirty... they replaced it for free since it was under the
> warranty... so i got 2 sensors for the price of one... paid $431...
> what a rip.... $279 for the sensor, and 2 hours labor...
>
> btw, had two codes present P0171 System too lean (fuel trim) and P1133,
> AF sensor circuit slow response malfunction (bank 1, sensor 1)


Toyota charge a lot for repair work,....then again the others a probably
little better. They all have to pay for the huge airconditioned showrooms
and offices.

Jason (got a $840 total bill for a cam-belt, idlers and oil-pump replacement
($238)


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Old 22 Jul 2003, 11:37 pm   #7 (permalink)
MDT Tech®
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Default Re: 97 4 Cylinder Camry with DTC P0171

marvin shostack wrote:
> Please help.
>
> My Check Engine Light has come on and I have determined that it was
> caused by Diagnostic Trouble Code P0171, System too Lean. There are no
> other codes and the car behaves normally in every respect.
>
> I don't believe I have a vacuum leak as the idle speed is correct.



You are not familiar with these cars then. Go ahead and remove that huge
vacuum hose going to your power brake booster. That will create a hug
air leak, now hang on for a few seconds, notice how good it runs? ECU is
adjusting injectro duration to compensate for it. So you probably do
have a lean condition or a failed MAF sensor.

>
> I don't believe the problem is low fuel pressure as the car has normal
> acceleration and does not bog.
>
> My theory is that I have a lazy Air/Fuel sensor (not called O2 sensor
> for California emissions). It seems to me that the only feedback the
> emissions control computer has that would cause a lean trouble code is
> the Air Fuel sensor.
>
> There is one more piece of information, the Fuel Trim indication was
> -11%. I am hoping that I can get some technical advice before I spend
> $240 on a replacement Air/Fuel sensor.


That means it was adjusting fuel. Are you sure it was negative? Freeze
frame date of -11% means it was reducing fuel by 11%. Normal is around
0% and corrections to about 8% +/- is normal. But over 10 is the sign of
some trouble. usually these lean codes are set when it hits closer to 16
and above.


You dont have a K&N filter in it, do you?

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Old 22 Jul 2003, 11:38 pm   #8 (permalink)
MDT Tech®
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Default Re: 97 4 Cylinder Camry with DTC P0171

Mark Uhlenkamp wrote:
> P0171 is most likly caused by a dirty or faulty Mass Air Flows Sensor. Dirty
> MAF Sensors are often caused by over oiled K&N air filters.
> MU
>
>
>


BINGO!

Philip, remember the K&N lackey? He'd hate to see this!

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Old 23 Jul 2003, 12:43 am   #9 (permalink)
Philip®
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Default Re: 97 4 Cylinder Camry with DTC P0171

MDT Tech® wrote:
> Mark Uhlenkamp wrote:
>> P0171 is most likly caused by a dirty or faulty Mass Air Flows
>> Sensor. Dirty MAF Sensors are often caused by over oiled K&N air
>> filters.
>> MU
>>
>>
>>

>
> BINGO!
>
> Philip, remember the K&N lackey? He'd hate to see this!


Ohhhhhhh... yah.
--

Philip

"If a long train of abuses, prevarications, and artifices, all tending
the same way, make the design visible to the people . tis not to
be wondered that they should then rouse themselves."
- John Locke (1632-1704)


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Old 23 Jul 2003, 11:04 pm   #10 (permalink)
Andrew
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Default Re: 97 4 Cylinder Camry with DTC P0171

YOu said it yourself, but make sure you verify instead of "think" that
you don't have problems in the vacuum and fuel pressure area. How's your
MAP sensor?

marvin shostack wrote:
> Please help.
>
> My Check Engine Light has come on and I have determined that it was
> caused by Diagnostic Trouble Code P0171, System too Lean. There are no
> other codes and the car behaves normally in every respect.
>
> I don't believe I have a vacuum leak as the idle speed is correct.
>
> I don't believe the problem is low fuel pressure as the car has normal
> acceleration and does not bog.
>
> My theory is that I have a lazy Air/Fuel sensor (not called O2 sensor
> for California emissions). It seems to me that the only feedback the
> emissions control computer has that would cause a lean trouble code is
> the Air Fuel sensor.
>
> There is one more piece of information, the Fuel Trim indication was
> -11%. I am hoping that I can get some technical advice before I spend
> $240 on a replacement Air/Fuel sensor.
>
> Thanks in advance.
>
> Marvin


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