No, this is wrong. The pedal on the floor adjusts the air flow, the computer does not. The computer ONLY adjusts the amount of gasoline being squirted into the cylinder.
If the air flow is more or less restricted, the throttle will have to be moved to a different position to get the same amount of fuel/air mix, but this is something that the driver does without thinking about it.
You appear to have a completely mistaken notion of how the system works. In addition, you are under the delusion that the system "learns" and somehow adapts to different conditions. It does not. The system uses short-term feedback for control. If a sensor fails, the feedback loop is broken.
This is probably true, but irrelevant and your problem has not been repaired. It will be back.
Are you saying the gas pedal is actually an air pedal? It indirectly affects the amount of gasoline? interesting..
I am not a car person so my assumptions may be completely incorrect.
It took several drive cycles before I started to notice the car sounded a little different with the KN filter, and took several drive cycles for the car to get back to normal after putting back a regular filter. To me that seems like learning.
Weren't there a lot of discussion about how disconnecting the battery will cause the car to relearn its operating parameters (even says on on my hays manual) and it may run rough for the first X number of miles, where some claim X is 50 miles and others say is hundreds of miles.
If the feedback and adjustment is instant, what is this learnign process? Search for ECU reset will show what I am talking about. Again I don't know what exactly is this "operating parameter". When I called Nissan for an MAF replacement estimate, the guy said they also have to 'retrain' the computer because of a new sensor. I probed him what exactly it is (or the process), he didn't really answer but it sounded like they use some instruments to clear or reset the ECU to have it relearn. Probably normal driving cycle would do the same but would just take longer.
It was actually slightly below freezing last night. The car started this morning without any trouble with idling or hestitation on acceleration. All of the symptons that I had in the last few days have disappeared. It IS the damn filter.
Put it differently, the damn filter is not compatible with my old aged car, where some components (say the MAF) may not be operating in peak condition. I don't know exactly what, but the KN filter is the cause.
It may very well be that if I replace the MAF sensor, my car would be able to work with the KN filter, but that's money that I definitely don't care to spend just to get a stupid $50 aftermarket 'performance improvement filter' to work. They should've designed one with the performance characteristic of the OEM filters but with the benefit of being washable and reusable.
I am even thinking this may be the cause of the urban legend of the KN filter messing up the MAF. It's not the OIL that's messing up the MAF as KN has demonstrated, it's the MAF, some of which are slightly out of tolerance, that can't work with the stupid filter. Of course putting in a brand new MAF sensor would mask/fix the problem, but probably there won't be a problem in the first place if regular filter is used. People have cleaned the MAF sensor and got better results, or so I've read, but likely that just brings the MAF sensor performance up where it does work with the filter.
Back in the old days, cars had carbs. The carb had a gadget to spray fuel into the air passing through it. The output of the carb went into a big butterfly valve that was adjusted by the gas pedal. The more you pressed the pedal, the more fuel/air mix went into the cylinder. The mix of fuel and air was set by the size of the jet in the carb. This system runs open loop with no feedback, so changing the jet size or the air flow will change the mixture.
When fuel injection systems came in, they were retrofitted into existing engine designs. The butterfly valve was kept unchanged, except that it now adjusted only the air mixture. An air volume or air flow sensor was used to tell how much air was going in, and an electronic (or sometimes hydromechanical system) adjusted the amount of fuel that the injector produced. This system has FEEDBACK. A change in any part of the system will be compensated for.
I strongly recommend you get the Chilton's book about basic car maintenance to get some idea of how this system works.
There are some cars that do this. Your car does not. There are cars for which the ECU is stateful but this is not one of them. Also, even if the system IS stateful, the air filter is not one of the things that it is going to have to adapt to.
Some cars have computers that adapt to certain parameters, most of which have more to do with the driving style than anything else.
On some cars, and your car might be one of them, the ECU has some fudge factors which are applied to individual sensors. This allows manufacturers to have very wide tolerance when they manufacture sensors. For the most part, though, these changes are relatively subtle and will NOT change severe drivability issues like you describe.
Could be, but I'd sure want to know what that "operating parameter" was, and I'd sure check the MAF and air plenum very very carefully before I came to any other conclusions besides the MAF. Of course, if you can't see the ECU data, you really have no idea what is really going on.
Some do behave in what would appear to be a learning condition. From the Ford 1997 MY OBD System Operation Summary for Gasoline Engines:
Misfire Monitor ... "Profile correction" software is used to "learn" and correct for mechanical inaccuracies in crankshaft tooth spacing under de-fueled engine conditions (requires three 60 to 40 mph no-braking decels after Keep Alive Memory has been reset). These learned corrections improve the high-rpm capability of the monitor for most engines. The misfire monitor is not active until a profile has been learned.
The problem could still be K&N related if the K&N oil has coated the hot wire or something of that nature. But if that's the case, it will probably come back. Another possibility is that he disturbed or incorrectly assembled something while changing the filter. This could be intermittent or might go away by changing the filter back because the error is not repeated.
It sounds to me like you dumped some oil into the intake when you removed the KN filter. That fouled one or more spark plugs. Then it took a little driving for the engine to "learn" how to run with clean spark plugs.
I'm going to have to agree with the others that the K&N isn't likely to blame.
If a 10% increase or decrease in airflow (which is about all a K&N will likely do) causes an error, then your car would be throwing errors every time you had a dirty air filter and/or replaced it with a clean one.
My car is a Pontiac, but here's how much "tolerance" there is in some setups: I am able to run a 100hp shot of nitrous into the airbox, and the MAF is able to run with that and give me 100hp extra worth of fuel. All I had to do was change spark plugs - that's my entire engine tune. (knocks a full second off in the quarter mile - 01 Trans Am in case you're wondering...)
FWIW, I also have a K&N on there, but that's only because for this car, it's barely twice the price of a regular paper filter.
Sorry I can't be more help, but I missed the original thread.
Went on the 2k mile road trip last week. The problem never came back. The service engine soon light did not come on, and the hesitation on acceleration from a stop never came back. The engine was running quite smooth the whole time.
Could be the KN filter, could be something else related to the change, I have no idea. I hope it stays this way.
That's absolutely true. And it was even true in the days of the carburetor. The pedal opens or closes the throttle butterfly valve, which regulates AIR flow. The increased airflow draws in more fuel through the metering jets (carburetor) or causes the MAF sensor to detect more air flow which tells the computer to squirt more fuel through the injectors (MAF EFI). In the case of speed-density EFI, its not quite as direct- opening the butterfly valve increases the manifold absolute pressure (MAP) reading, and that combined with the current engine RPM measurement tells the computer how much fuel to squirt.
The minor exception to the gas pedal actually being an "air pedal" is the accelerator pump on a carbureted engine. That's an auxiliary mechanism whereby pushing down on the "gas" pedal really does cause an extra squirt of gas to be injected into the engine to prevent lean hesitation- but the main fuel flow is actually caused by the increased airflow.
The pedal opens or closes the throttle butterfly valve,
========= I have neither a MAF sensor or K&N filter, but from what I've read, the oiled K&N can foul the heated (?) wire in the mass airflow sensor, hence the source of the problem. Maybe there's a user tendency to over oil them. In any event, my standard response for K&N in daily use is:
From: Matthew E. O'Toole ( snipped-for-privacy@ix.netcom.com) Subject: Re: K&N air filter? View this article >
I've used K&N filters over the years too, and while the results you cite are not contrary to my experience, I am concerned about recommending these for everyday use in a passenger vehicle. I have done oil analysis on every car on which I've used a K&N. On all 6 cars, this showed many times the amount of silica particles (airborne dust) in the oil than when a paper filter was used. This means that the K&N does not do as good of a job filtering the air, allowing more dirt into your engine. You may very well experience increased engine wear due to this, as your oil filter will not catch it all.
Notice that K&N does not advertise their product as offering "better filtration", only as offfering "better flow". The K&N is a good product for it's intended use, which was not originally long term use in a passenger vehicle.
Some cars use hot wire anemometers for airflow, others use a moving vane attached to a potentiometer. I am thinking the original poster's car is the latter. They both can gum up and get sticky, but they do it differently and the failure indications are different.
That has been pointed out many times in the thread, and is likely quite true.
The counter-evidence here is that the problem would come and go and apparently was drastically altered immediately (for the worse) by replacing the K&N with a paper filter in a parts-store parking lot. That is not consistent with a fouled MAF which would remain fouled to the same degree right after a filter change, and might sloooooowly recover over time as the oil fouling evaporated off the hot wire. Sudden change after touching the intake plumbing is more consistent with a leak somewhere in the plumbing downstream of the MAF, or with a faulty electrical connection in the vicinity of the MAF, TPS, or some other intake-related sensor.
True... but I missed any reference to spilling oil into the intake. K&N filter oil is very light stuff and not at all likely to foul plugs. I doubt you could foul the plugs even if you sprayed half a cup of the stuff straight into the intake of a running engine.
Hmm, this does sound like a reasonable explanation. My thought on why the highway miles fixed it was the highway drive set some high point in the system learning data (whatever it may be, I have no idea as I really know nothing about cars but I am a software guy). Driving locally doesn't provide enough dynamic range for the system to properly set itself after a filter change with restricted air flow, comparing to what the KN was giving.
To the best of my knowledge I did not and could not have fixed a lose connector or something. Everything I touched, including my failed attempt to twist off the MAF, was before the MAF chain. I did not touch anything after the MAF.
That would be a disaster won't it? The manual warns of burning if no filters are installed due to engine back fire? Yes the engine was off when the filter was swapped.
But why would the fouled plug worked OK with the KN filter? When I installed the KN filter, the engine sounded different after a few drives with the KN filter, not immediately. That's where I got my theory that it takes a few drive for the thing to full adapt (a few drive that involves both low/high speed perhajs). I never did highway drive after I put back a regular filter, until the 15 minutes drive to the mechanic after which the car fixed itself. It idled rough, even when I disconnected the battery overnight. (hey, I am a software guy, when in doubt, reboot. ;)
I guess I could repeat the experiment by trying the KN filter again, drive for a few days, then switch to regular filter and see how it idles. But I probably won't do it because my car is kind of old and there really isn't much I know how to do on cars when problems do occur... ;)
On my other car, after I changed the spark plug (the original ones had been in there for 10 years probably), the engine was quite loud when I initially started the car. I was like, oh crap, did I mess somethig up? Then it quiet down relatively fast, and that loudness never returned on startup. So this type of learning seems pretty fast.
I am just not sure about the other type of learning with the filter change, and what exactly it is learning and adapting. My guess is the airflow changes requires a change in fuel spray, which seems somewhat related to the "system too rich" code after a battery disconnect and highway drive with the KN filter.
That's the single silliest thing I've ever heard in my life. Or at least very close to it. But then it IS a Haynes manual, too.
Well, I suppose its like saying "you might be struck by lightning if you carry an umbrella on a sunny day." It COULD happen, but the odds are astronomically against it.
You change your air filter with the engine running? It's either in the Hays manual, or printed somewhere near the air filter in the car. I remember seeing it every time I change the air filter. Maybe I should take a picture for you to enlighten you.
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