Oiled filter and CEL code P0172
 

Has anyone else experienced a CEL with code P0172 (too rich) while using a K&N or other oiled filter? Mine has done it 3 times now. I've cleared the code and cleaned the MAF sensor, and it'll be fine for a week or two before throwing the code again.



Supposedly, oil build up on the MAF sensor is a myth, if you believe K&N. But as a test, I put the stock filter back in last night. I'll keep you posted.



It's possible that I have a faulty MAF sensor as well, but I haven't been able to find a replacement yet outside of the dealership. Anyone have a source? I haven't checked with the dealership yet to see how much they want for one, but it's not likely to be cheap.

I have K&N air filter for the past 10k miles. No CEL or anything. Is your car completely stock aside from the air filter? If you are stock, try putting the stock filter back in like you said and run it for a few weeks. If the CEL still comes on, then go to the dealership and ask them to check it out.

The obvious question is whether the filter feels like it's over oiled? It should be a very thin film. Did much oil come off the MAF when you cleaned it?

Probably clogged up MAF with oil

What is the basic steps to clean out MAF sensor. spray it with cleaner and let it dry for how long?

is it a dangerous procedure?

I have a K&N and never had issues. Have you checked if you closed the airbox right? I know that can be a pain and I had issues closing it. Are all the pipes and hoses well installed. Could be an air leak.

I hope you didn`t oil your filter before installing? Because they come pre-oiled and it should not need more oil.

Definitely not a myth, car community I come from (MKIII Toyota Supra) it's well known that oiled filters damage the airflow meter (it's a Karman Vortex AFM that can't be cleaned).


Keep in mind that "The World's Best Air Filter" is a trademark by K&N, and not true :)

No, I did not oil the filter. It's right out of the box. It doesn't appear to be over oiled, but there was a thin film inside the housing when I took it out.



Closing the filter box crossed my mind. I've never had a car on which it was as unwieldy as this one. It's possible I didn't have it completely sealed at the bottom.



The car is not stock. I do have a Unichip installed, with the all drop-ins map. This could be a consideration too, but I've had it on there for almost a year, and this issue just started within the last month. But I've probably had the K&N for the last 8 months too.



As for cleaning the MAF sensor, it's simple. Unplug it, remove 2 screws, and pull it out. You can buy a can of cleaner at any auto parts store for $10. Spray it all over. It dries almost instantly. You couldn't put it back in before it would be dry.



I'll run the stock filter for a couple of months, and then if the CEL stays off. I'll put the K&N back in and see what happens. At least that will tell me if the sensor is at fault.

It may have been Unichip. Try removing that and resetting the battery to see if you still get CEL with the K&N. I have no tune and I haven't gotten a single CEL with the K&N. If anything, it may be the Unichip maps that are causing the car to run rich. The ECU should automatically adjust after a while at stock I believe.

I have the Unichip and I got the P0172 everyday for ~6 months. I took out my Injen Cold Air Intake back to the stock intake and now I don't get it anymore. Which maps are you running on your Unichip? I'm running the 93 octane Drop in + catback fuel standard time + and I haven't had the P0172 for a week now.

Actually don't use brake cleaner or parts cleaner, they sell a specific one called a Mass Air Flow cleaner.

Having oil on the MAF from using an K&N is pretty common on vehicles that use a MAF system. Thats the first thing I look for, an over oiled filter when I look for that code.

Keep in mind the MAF has 2 wires inside, and the 2nd one that the computer uses as the sensor is covered in debris and oil which causes the wrong reading. DO NOT use a brush or touch it to clean it.

I don't think the Unichip is at fault. Using a reader, once the P0172 is thrown, I can see that the Long Term Fuel Trim is at -30%. Once I clean the MAF and drive it a little bit, it drops bank into the single digits to around -10%. Nothing in the Unichip has changed, leading me to believe that the MAF sensor was under-measuring the airflow.

Besides, if it comes down to getting rid of one or the other, adios K&N. I've been back to the stock filter for about a week now, and don't really notice any difference vs. the K&N. On the other hand, the Unichip has a very noticeable affect on performance. The only way I'd get rid of it would be if I decided to go with a full tune.

@davidchoi, I'm running the 93 octane, all drop-ins, standard fuel and timing map. Nothing aggressive at all.

BTW, on the upside to all of this, I discovered yesterday that MAF sensor cleaner is excellent at removing melted crayon from cloth seats. My son left a red crayon in the front seat of my daughter's car (not mine, thankfully!), and it melted into a red pool. I wiped off what I could, but there was still a big stain. On a whim, I sprayed a small spot with the MAF cleaner, and the crayon disappeared! Once I was sure that it wasn't going to bleach out the upholstery (black velour, just like mine), I sprayed the entire thing and wiped it up with a cloth towel. No trace left!

Interesting. Before pulling out my Injen cold air intake I tried everything (to desperately keep the CAI on), one of the things I tried was cleaning my MAF sensor with MAF sensor cleaner. No difference at all in feel and still got the CEL within an hour after cleaning. Someone also replied to my post on another thread saying s/he has had the same intake installed as me + the unichip with no issues. It's interesting how differently our cars react to mods.