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Engine runs rough above 40 mph
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CarGuru > Open discussion > Engine runs rough above 40 mph 9 May 2005 18:44:02

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Engine runs rough above 40 mph

M Long via CarKB.com 3 May 2005 16:40:15
 I have a 1991 Lexus es250 126000 mile engine that runs rough above 40 mph
for a while, then runs smooth, then runs rough. Mechanics tuned it up and
replaced spark plugs,ignition wires, distributor, rotor, air flow meter,
air filter, alternator belt. None of which solved the problem. Thanks for
any suggestions.
Add comment
Blk Knight 3 May 2005 17:04:22 permanent link ]
 See if there are any codes stored in the computer, could be a sensor.

--
Ed Smith"I came into the world with nothing and I still have most of it"
"M Long via CarKB.com" <forum@nospam.CarKB­.com> wrote in message
news:b5ec3da592a54f­e3ad861796e15e97da@C­arKB.com...>I have a 1991 Lexus es250 126000 mile engine that runs rough above 40 mph> for a while, then runs smooth, then runs rough. Mechanics tuned it up and> replaced spark plugs,ignition wires, distributor, rotor, air flow meter,> air filter, alternator belt. None of which solved the problem. Thanks for> any suggestions.


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M Long via CarKB.com 4 May 2005 06:51:18 permanent link ]
 There are no codes stored

--
Message posted via http://www.carkb.co­m
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Mrcheerful . 4 May 2005 15:31:53 permanent link ]
 
"M Long via CarKB.com" <forum@nospam.CarKB­.com> wrote in message
news:b5ec3da592a54f­e3ad861796e15e97da@C­arKB.com...>I have a 1991 Lexus es250 126000 mile engine that runs rough above 40 mph> for a while, then runs smooth, then runs rough. Mechanics tuned it up and> replaced spark plugs,ignition wires, distributor, rotor, air flow meter,> air filter, alternator belt. None of which solved the problem. Thanks for> any suggestions.

internally broken exhaust, esp. cat converter, may give those symptoms.
have you had the fuel filter changed, again that is a possibility.

mrcheerful


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M Long via CarKB.com 5 May 2005 00:56:05 permanent link ]
 Check engine light came on today when I got to 55 mph. It was codes
25 and 26. According to the manual, codes 25,26 have the following in
common;engine ground bolt loose,open or short in injector circuit, fuel
line pressure,open or short in oxygen sensor circuit,oxygen sensor,water
temp sensor,foreign object caught in valve, and ECU.
What would be the most likely cause?

--
Message posted via http://www.carkb.co­m
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Ray O 5 May 2005 01:33:25 permanent link ]
 
"M Long via CarKB.com" <forum@CarKB.com> wrote in message
news:7146a65b044f49­d3b3778509268a485c@C­arKB.com...> Check engine light came on today when I got to 55 mph. It was codes> 25 and 26. According to the manual, codes 25,26 have the following in> common;engine ground bolt loose,open or short in injector circuit, fuel> line pressure,open or short in oxygen sensor circuit,oxygen sensor,water> temp sensor,foreign object caught in valve, and ECU.> What would be the most likely cause?>
-- > Message posted via http://www.carkb.co­m

Most likely causes are oxygen sensor and loose ground bolt/poor connection
to ground.
--
Ray O
correct the return address punctuation to reply



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M Long via CarKB.com 5 May 2005 04:40:49 permanent link ]
 I ordered an O2 sensor for $67.00. With 126000 miles I guess it needs to be
replaced good or bad. Hopefully this is the problem. Thanks for your
suggestion.

--
Message posted via http://www.carkb.co­m
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HarleyVA@nospam.net 5 May 2005 05:52:49 permanent link ]
 On Wed, 4 May 2005 16:33:25 -0500, "Ray O"
<rokigawa@tristaras­sociatesDOT.com> graced this newsgroup with:
"M Long via CarKB.com" <forum@CarKB.com> wrote in message >news:7146a65b044f4­9d3b3778509268a485c@­CarKB.com...>> Check engine light came on today when I got to 55 mph. It was codes>> 25 and 26. According to the manual, codes 25,26 have the following in>> common;engine ground bolt loose,open or short in injector circuit, fuel>> line pressure,open or short in oxygen sensor circuit,oxygen sensor,water>> temp sensor,foreign object caught in valve, and ECU.>> What would be the most likely cause?>>
-- >> Message posted via http://www.carkb.co­m>
Most likely causes are oxygen sensor and loose ground bolt/poor connection >to ground.


also your mass airflow sensor...probably with that mileage, it's
dirty.
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Ray O 5 May 2005 07:45:29 permanent link ]
 
"HarleyVA@nospam.ne­t" <bounce@bounce.net>­ wrote in message
news:i2vi71tioqetio­9cgp6f9icildqc9k5dje­@4ax.com...> On Wed, 4 May 2005 16:33:25 -0500, "Ray O"> <rokigawa@tristaras­sociatesDOT.com> graced this newsgroup with:>
"M Long via CarKB.com" <forum@CarKB.com> wrote in message>>news:7146a­65b044f49d3b37785092­68a485c@CarKB.com...­>>> Check engine light came on today when I got to 55 mph. It was >>> codes>>> 25 and 26. According to the manual, codes 25,26 have the following in>>> common;engine ground bolt loose,open or short in injector circuit, fuel>>> line pressure,open or short in oxygen sensor circuit,oxygen sensor,water>>> temp sensor,foreign object caught in valve, and ECU.>>> What would be the most likely cause?>>>
-- >>> Message posted via http://www.carkb.co­m>>
Most likely causes are oxygen sensor and loose ground bolt/poor connection>>to ground.>
also your mass airflow sensor...probably with that mileage, it's> dirty.

Good point!
--
Ray O
correct the return address punctuation to reply


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Ray O 5 May 2005 07:46:28 permanent link ]
 
"M Long via CarKB.com" <forum@CarKB.com> wrote in message
news:912ec2889a3841­80870e87f89e25ac5d@C­arKB.com...>I ordered an O2 sensor for $67.00. With 126000 miles I guess it needs to be> replaced good or bad. Hopefully this is the problem. Thanks for your> suggestion.>
-- > Message posted via http://www.carkb.co­m

To clarify, I doubt if the O2 sensor would cause the engine to run rough but
it cold solve the check engine light.
--
Ray O
correct the return address punctuation to reply


Add comment
M Long via CarKB.com 5 May 2005 16:04:16 permanent link ]
 The air intake sensor was replaced with the air flow meter. Also about 10
months ago the fuel pump,fuel filter and gas tank were replaced.The gas
tank had rusted and clogged the fuel lines. The gas tank was replaced with
a used gas tank.

--
Message posted via http://www.carkb.co­m
Add comment
Ray O 6 May 2005 09:59:40 permanent link ]
 
"M Long via CarKB.com" <forum@CarKB.com> wrote in message
news:79232656b88147­248d987dc12ae1a895@C­arKB.com...> The air intake sensor was replaced with the air flow meter. Also about 10> months ago the fuel pump,fuel filter and gas tank were replaced.The gas> tank had rusted and clogged the fuel lines. The gas tank was replaced with> a used gas tank.>
-- > Message posted via http://www.carkb.co­m

I forget what type of vehicle you have, but an air intake sensor serves the
same purpose as an air flow meter. I doubt if your car has both.

Are the ignition wires and spark plugs OEM parts or aftermarket parts?
--
Ray O
correct the return address punctuation to reply


Add comment
M Long via CarKB.com 6 May 2005 20:30:41 permanent link ]
 A mechanic installed the wires, they have Japanese letters on them.I was
going to replace them myself until I saw I would have to remove the air
intake chamber to get to the 3 in the back. Looking at the manual for my
1991 Lexus ES250 page FI-37, the air flow meter has an air temp sensor
built into it. The O2 sensor should arrive today so I'll see if it fixes
the problem. Also could the PCV valve cause this problem?

--
Message posted via http://www.carkb.co­m
Add comment
Ray O 6 May 2005 21:05:24 permanent link ]
 
"M Long via CarKB.com" <forum@CarKB.com> wrote in message
news:90d86bbce56e4a­7584e1d36d1739609a@C­arKB.com...>A mechanic installed the wires, they have Japanese letters on them.I was> going to replace them myself until I saw I would have to remove the air> intake chamber to get to the 3 in the back. Looking at the manual for my> 1991 Lexus ES250 page FI-37, the air flow meter has an air temp sensor> built into it. The O2 sensor should arrive today so I'll see if it fixes> the problem. Also could the PCV valve cause this problem?>
-- > Message posted via http://www.carkb.co­m

Genuine Toyota/Lexus ignition wires will say Toyota or Lexus or Nippon Denso
or ND. Come to think of it, I don't think genuine Toyota/Lexus wires have
Japanese writing on them.

I'm not sure why, but Toyota/Lexus seem to run poorly on aftermarket
ignition parts - plugs, wires, rotor, etc. Many of these kinds of
driveability problems are solved by installing OEM ignition parts.

I suspect that what you think are Japanese letters are actually Chinese.
Many of the 8,000 characters are identical in Japanese and Chinese so
someone who cannot read either language would have a very difficult time
telling the 2 apart.

I thought you had called it an air flow sensor, not an air temperature
sensor. A bad air temperature sensor is unlikely to cause the drivability
problems you are describing.

I doubt if replacing the O2 sensor or PCV valve will solve the problem. I'd
start with genuine Toyota or Lexus ignition wires and plugs, cap, and rotor.
Also, make sure that the base ignition timing is correct and that it is
advancing correctly.
--
Ray O
correct the return address punctuation to reply


Add comment
Jyrki Alakuijala 9 May 2005 18:44:02 permanent link ]
 Ray O wrote:
I doubt if replacing the O2 sensor or PCV valve will solve the problem. I'd

My Lexus LS 400 1994 had the same symptoms. I replaced the PCV and
changed the air filter. No improvements. I had two faulty O2 sensors,
ignition wires and plugs replaced by the official Lexus shop using
official parts. The engine seemed to run rougher below 1500 rpm than
before, but had no problems above 75 km/h as it used to. I guess the
O2 sensors were the most important factor in the improvement. However,
gas consumption went up from 13 l / 100 km to around 14.5 l / 100 km
when the "repair" was done.

Now, after about 6 months and 5000 km, the symptoms are back. Car
runs a bit rough above 60-75 km/h.

Next, I am planning to replace the throttle position sensor (or actually
swap the "unused" TPS from the ESP with the normal throttle TPS). Is
this a good idea?

Emissions measurements (3rd party) were fine before and after the
repair.

If someone knows the proper fix for this, I would be very pleased to
hear about it.
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CarGuru > Open discussion > Engine runs rough above 40 mph 9 May 2005 18:44:02

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