I have check engine light, the code pulled is a P1131, I changed out the
mass air flow sensor, and the light will stay off for about 50 miles and
come back on. I have replace the new one and the same thing happens again.
I even changed the small wire harness that goes to the sensor. any and all
advice is deeply appreciated
Your DTC indicates that the PCM is correcting for an overly lean
condition..... possible causes... "unauthorized" (unmeasured) air, vacuum
leaks, low fuel pressure or volume.... I don't know why you continue to
browbeat the MAF..... I'd probably start with a new fuel filter and work
You are an eager student of human behavior, so perhaps you can explain this
to me. Why so many people prefer to spend a lot of money on far-fetched
propositions instead of first assuming that sensors might simply be telling
See the '96 Ford Thunderbird...' posting just below this one if another,
even more convincing example is needed. That gentleman replaced just about
anything, except for what might have been causing his lean condition.
I have even spoke with a few of the local service centers and they also
said the the sensor was bad, Since I dont do this as my full time job I
have to seak the possible wisdom of the local services centers and then I
found this web site. hoping I can get this thing beat
Most codes need to show a pattern of repetition before they will set. This
is necessary to avoid nuisance codes..... For some codes, the condition has
to last a perscribed amount of time... other codes must happen at least
twice and even others need to occur on consecutive drive cycles before the
light sets and a code is saved to memory. This is in regards to memory
codes. On demand codes need to have the problem occur when the self-test is
It's not for me to say if your local service centres are right or wrong in
their prognosis... but I see that your problem has recurred even after parts
replacement. Fords description of the codes hasn't changed since I last
replied.... The PCM is trying to adapt to a lean condition and apparently
can't. Addressing the MAF sensor doesn't seem to have fixed anything....
the light staying off for an extended period after replacing the jumper
harness may or may not be a red herring.
At this point, I would be accessing the O2 sensor PIDs ( a capable scan tool
is required) and see what the exhaust is doing as well as being sure of what
the short and long term fuel trims are telling me. As I'd mentioned....
vacuum leaks, fuel pressure or volume concerns, unmetered air are some of
the conditions that can deliver your concern. These conditions need to be
considered in any diagnosis of your problem.
I'm trying to help you..... don't be alarmed if I sound a little harsh
sometimes... this is my nature. Effective auto repair is nothing more than
applying a logical progression to a diagnostic scenario....
No worries Jim,
last night I change all the rubber vacuum hoses I could get to, there is
one surrounded by the intake maniflod an the PCV that I could not get to I
will call Ford for the PCV hose and also a new groumet for the PCV, since
it looks premolded. I did recheck the air intake ducts and even ran the
engine and sprayed carb cleaner at all of the joints, listen to hear if
the engine idle up or down. the engine ran smooth.
there has been no major work on the enigne. It is due for a new timing
belt. the only scan tool I have is a Actron OBDII Auto scanner CP9135, I
have been looking for PC software that gets more involved at the vehicles
performace, but have not found any bellow 500.00.
the truck has 166,000 miles on it.
I do have a CP7818 Fuel Pressure gage I can also make long hose assembly
for High Presure teflon so I can see what its does under demand, if the
fuel pump is out putting good strong volume then the pressure should be
sorry for the long rambles
Yes.... wide open throttle at highway speed should deliver the same pressure
as key on engine off.... not sure what it is in your instance but, if you
need, I can check.... usually 40 or so psi but there are those that are
different. If nothing else, we can eliminate this as part of the concern.
Here's the reasoning and an explanation of why a fuel pressure regulator (or
some other means of regulating the pressure) is required. These fuel
injectors are designed to give a particular spray pattern and atomization
size but this ideal condition only happens when the pressure drop across the
injector nozzle is at a predetermined value. When intake manifold vacuum is
high (much vacuum), the fuel pressure is reduced to maintain the ideal
pressure difference. When intake manifold vacuum is low (wide open throttle,
high engine loads), fuel pressure is increased to maintain the desired
pressure drop. Additionally, the PCM knows how much fuel will flow through
the injector at this pressure differential and computes injector on time
using this "known" value. It can learn changes in the fuel delivery, but it
can only compute so far before it decides that something is wrong that it
can't compensate for. At this time, it defaults to preset values and turns
on the CEL.
There are many tests that it would be nice if you had the means to perform
them... as it is, we can try to do those that we can and minimize the pain
in your hip pocket...
I replace the fuel filter every oil change around 3500-4000 miles I run 89
octane, the fuel sysem was clean by Tire Discounters about 6000 mile ago,
when I changed out the small harness the light stayed off for weeks then
it came back on
I noticed something weird while getting on the interstate when I stepped on
I loss vacuum to the ac controls the a/c was blowing out the dash vents but
then it started to blow out thru the window defrost vent, it slowly came
back to the dash vents where the control was still on the dash?
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.