Yeah, while I don't use K&N on anything, there's nothing evil about them per se - it's the oil used on them and any other oiled filter that's the culprit with the MAF sensors.

Most people don't read the instructions which tell you to use very little oil and let dry for several hours before use.

Are MAP systems still used or are most vehicles now using MAF systems?

I'm pretty sure my truck has both.

My truck has a MAP system....and people wonder why my Hemi gets 13 MPG, while my brothers '04 F150 will get 17-18 with a 5.4....

??

MAP is techonlogy from the 70s...yet that is what Chrysler still uses.

Well, yeah, it's that, plus the fact that K&N's pass FAR more dirt through them than a factory filter does...plus, once they trap a small amount of dirt, they don't flow any better so that small advantage is gone, too.
Good air filter test
Another one
Quote from the second link:


No, thanks. I'll stick with a factory filter.

I missed this thread somehow, and a good one it is. I have a lot to add on this subject, but not tonite. Stay tuned.

I am on pins and needles!

I'm pretty sure even a MAF system uses a MAP signal.

One thing that gets overlooked is Oxygen sensors, they can cause excessive fuel consumption also, they should be replaced about 80,000 miles I think.

I've thought about replacing my O2 sensors, but 4 of 'em are spendy!

First off, don't arbitrarily (sp?) replace 02 sensors on 96 and newer vehicles - the systems are very sensitive and the computer will flag a lazy or faulty 02 sensor and set a code, unlike years ago where replacing an 02 sensor on a high mileage engine would yield a notable fuel mileage increases or better driveability.

Rear 02 sensor(s) (aft of a catalytic converter of course) job is only to be a tattletale on the converter's efficiency and are not used in adjusting air/fuel ratios. They are found on some late 95's and all 96 and newer cars and light trucks.

Next, F14's MAF sensor woes are of the internal circuit board variety - just poor durability. Some of the 80's GM 6-cylinders had a TSB where we would convert from a problem-prone MAF system back to the MAP system. MAP, at that point, was more reliable but not as fine-tuned as a MAF system, hence loss of performance and fuel mileage were a real potential after a conversion.

As far as cleaning the newer MAF's are concerned, the folks at the pinnacle of training and diagnostics DO NOT RECOMMEND cleaning MAF sensors!

I won't get into the long-winded reasons, but my position continues to be TO clean them!

I have cleaned 100's of them using spray carb clean and a soft tootbrush, and a magnifying glass easily shows the before and after results.

Dirty MAF sensors can cause poor fuel mileage, hesistation, unstable idle and other issues. The dirt build-up skews the data from the sensor.

On the Fords, be sure to reset the KAM (keep-alive memory) by disconnecting the battery cables and putting a jumper-lead between them (cables) for 30 seconds or so. Most Fords don't use a baro sensor, as baro is inferred from the MAF. If you had a scantool, you can note the baro before and after cleaning.

The 2 wires shown in Mike's picture show the sensing wire and reference wire. The side towards the air filter will always be the dirty side. Always use a high-quality air filter. K&N filters are suppose to be bad for the MAF sensor, but I can honestly say that I haven't seen a problem with K&N's and MAF's.

Besides Ford, I have cleaned many GM's, where the 3-piece sensor has to be disassembled, many Toyotas and Nissans too.

Be sure to get all of the duct work, lines and connectors back together and tight, if you tackle this job yourself. Windstar and some F-series trucks "hide" the sensor in a conical housing between the throttle body and air filter. A more difficult job, but the results will be the same. Be sure to get the big, rubber wiring plug secured back into the housing or you will get the dreaded P0171 and P0174 system lean codes.

I guess I should get into some of the reasons why the experts say not to clean them. First, they say there is no way to verify that the sensor is performing back to OEM specs. It is just too sensative to be field-serviced. Testing on a flow-machine is the only way to verify that it is. Overtorquing the screws, etc, throws the unit out of calibration.

The other big issue at the heart of the clean vs no-clean debate is that if you know the MAF is "bad", it should be replaced. If you are not so sure, then cleaning is a diagnostic "guess", they say.

Along the same lines, some say the reason for MAF sensors getting dirty in the first place is leaking contaminates from the sensor itself, which attracts the dirt, so cleaning only bandaides the real problem.

Again, I am on the "clean" side of the debate.

Terrific information, Bob - much appreciated!