1996 Ford Ranger 4 banger engine check engine light

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
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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 from there.

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Jim,
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 the truth? 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.

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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
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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 being run.
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....

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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 steady?
sorry for the long rambles
Al
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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...

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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
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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?
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That would indicate a vacuum leak.
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