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posted on October 20, 2006, 6:33 pm
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I have a 1995 F150 4X4 with a 5.0 Automatic. It runs fine sometimes but then
it will bog under part throttle, pop back and run crappy until wide open
throttle then it takes off and runs great. Always runs great at wide open
throttle. Occasionally it will stumble at an idle but most of the time it
idles perfect. It gives a lean code but as it is obd 1(stupid as I call it)
no data stream. Here is what I have done so far. A lot of this is as it is
my sons first truck and I just want it all ready as soon as he gets his
license in the next month.
New plugs, wires, cap, rotor & distributor
Changed computer - same exact symptoms as the original one
Fuel pressure test while driving on two tanks all is fine
New mass air
New fuel filter
New throttle position sensor
Cat is punched out
O2 sensor was replaced before I got it
Cleaned all grounds
It doesn't skip or run bad on any cylinder but just like something is not
telling the injectors to open all of the way until you hit wide open
throttle then it goes great.
It is worse up a hill but will do it on the flat also. The check engine
light will cycle on and off but only shows the lean bank 1 code. I am hoping
the different computer may come up with a new code.
Thanks in advance for all of your suggestions!
--
Why just do a job when you can OVERKILL it!
Re: 1995 F150 Help - Can not fix!
LOOK2X wrote:
Lean is lean. I'd be careful if it is truly having trouble with a
cylinder as you could fry an exhaust valve or a piston if the cylinder
isn't getting enough fuel.
Have you got a code scanner? Have you run the cylinder balance test to
check for a weak cylinder?
Beyond that, understand that at WOT, the engine computer goes into open
loop mode where it basically ignores the oxygen sensor input and just
uses some tables it stores and just pushes fuel out the injectors like
crazy. Try wot in a building and you'll smell the unburned fuel.
So if this is at part throttle, it would lead me to think perhaps an
issue related to computer control. I would recommend making sure that
the cooling system is functioning properly and that the sensors that
check coolant temperature are working. This is an input to the
computer.
I'd try running with the MAF sensor disconnected to see how it does and
if the behavior changes any. Without the maf sensor you'll get a check
engine code but the computer will use defaults and should run o.k.
After that you have to consider a possible issue like a bad distributor
or worn distributor allowing too much movement.
Re: 1995 F150 Help - Can not fix!
"LOOK2X" wrote: 1995 F150 4X4 5.0 Automatic.
Runs fine then will bog under part throttle, pop back and
run crappy, always runs great with WOT. Occasional
stumble at an idle but most of the time idles perfect.
Gives a lean code (OBD-I). Here is what I have done:
New plugs, wires, cap, rotor & distributor
Changed computer - same exact symptoms as the original one
Fuel pressure test while driving on two tanks all is fine
New mass air
New fuel filter
New throttle position sensor
Cat is punched out
O2 sensor was replaced before I got it
Cleaned all grounds
_______________________________________________
Possibly loose bolts holding throttle body, or sticking IAC.
Good luck.
Rodan.
Re: 1995 F150 Help - Can not fix!
Punched out cat can affect exhaust temp, which is what an
O2 sensor measures. Its nothing more than thermocouple
like on a hot water heater. If the exhaust is to cool
its voltage out put will be low which tells the ecm its running rich,
so the ecm leans out the fuel mix, which raises combustion temps which
can cause back fires. WOT, the O2 is ignored.
How many O2's on this model?
Whitelightning
Re: 1995 F150 Help - Can not fix!
On Sun, 22 Oct 2006 02:08:36 +0000, Whitelightning rearranged some
electrons to form:
That is not correct. The O2 sensor measures the presense of oxygen
via an electrochemical reaction on a ceramic element. It is not
a thermocouple.
http://patft.uspto.gov/netahtml/PTO/srchnum.htm
Patent # 3933028
--
David M (dmacchiarolo)
http://home.triad.rr.com/redsled
T/S 53
sled351 Linux 2.4.18-14 has been up 24 days 10:17
Re: 1995 F150 Help - Can not fix!
On Sun, 22 Oct 2006 03:13:13 +0000, Whitelightning rearranged some
electrons to form:
I haven't tried this, but the theory says that since the chemical reaction
doesn't occur unless it's hot, you would have to heat it with a propane
torch, or something like that. When it was in the flame, it should
indicate rich, or centered (since the propane was consuming the oxygen)
and out of the flame, it should indicate lean (lower voltage) until it
cools off, then it would read nothing.
YMMV
--
David M (dmacchiarolo)
http://home.triad.rr.com/redsled
T/S 53
sled351 Linux 2.4.18-14 has been up 24 days 18:28
Re: 1995 F150 Help - Can not fix!
PS, you left out your statement from earlier:
On Sun, 22 Oct 2006 02:08:36 +0000, Whitelightning rearranged some
electrons to form:
Punched out cat can affect exhaust temp, which is what an
O2 sensor measures. Its nothing more than thermocouple
like on a hot water heater.
--
David M (dmacchiarolo)
http://home.triad.rr.com/redsled
T/S 53
sled351 Linux 2.4.18-14 has been up 24 days 18:44
Re: 1995 F150 Help - Can not fix!
On Mon, 23 Oct 2006 02:50:40 +0000, Whitelightning rearranged some
electrons to form:
Perhaps, but you're original statement is still wrong.
An O2 sensor is
*not* a temperature sensor. It measures the partial pressure of oxygen.
It requires heat for the chemical reaction to occur between the oxygen and
the ceramic element. At a given temperature, it will output a different
voltage based on the oxygen content of the gas around it. If you heated
it with a heat gun, the voltage will drop as the sensor cools off, as the
chemical reaction stops... thus the reason that most O2 sensors have a
built-in heater so they will come up to temperature quickly.
Don't believe me? Read it yourself:
http://auto.howstuffworks.com/question257.htm
A thermocouple is a junction of dissimlar metals, which generates a
very small voltage (millivolts) based on temperature based on the Seebeck
effect. The presence or absence of oxygen has no effect on a thermocouple.
http://en.wikipedia.org/wiki/Thermocouple
There are many more references out there, if you'll take the time to
search.
--
David M (dmacchiarolo)
http://home.triad.rr.com/redsled
T/S 53
sled351 Linux 2.4.18-14 has been up 25 days 17:04
Re: 1995 F150 Help - Can not fix!
On Mon, 23 Oct 2006 09:23:42 +0000, David M rearranged some electrons to
form:
Here's some more:
http://www.omega.com/thermocouples.html
http://www.boschautoparts.com/FAQs/default.htm (select oxygen sensors)
--
David M (dmacchiarolo)
http://home.triad.rr.com/redsled
T/S 53
sled351 Linux 2.4.18-14 has been up 25 days 17:29
Re: 1995 F150 Help - Can not fix!
I concede the point that they are 'different" devices. I can learn
and admit when I am wrong.
However, if the temperature isn't correct it is going to read wrong.
What is hard to understand here is the bank one lean error code.
If there is only one O2 sensor, how can the system determine
a lean bank?
Whitelightning
Re: 1995 F150 Help - Can not fix!
On Tue, 24 Oct 2006 01:02:10 +0000, Whitelightning rearranged some
electrons to form:
Correct, that's why they have a built-in heater to get them up to
temperature quickly. Older ones didn't have the heater and thus
ran open-loop until the engine warmed up, spewing a lot of unburned fuel.
I can't remember the exact number, but a model from this decade (2000's)
has something like 100 times cleaner emissions than something from 20
years ago.
It probably has more than one sensor. My OBD-II '98 has four.
I haven't had to change them (yet) after 123k on the clock.
I've replaced the one on the wife's '94 Jeep twice in the past 12 years,
though. Go figure.
--
David M (dmacchiarolo)
http://home.triad.rr.com/redsled
T/S 53
sled351 Linux 2.4.18-14 has been up 26 days 16:55
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