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      01-03-2012, 04:14 PM   #1
FifthStreetz
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Oiled air filters and MAF sensor/Idle control sensor

So ive been using oiled air filters since my break in. Been about 20K miles now and I noticed that when i rev the car lightly in neutral (fully warmed up) the RPMs drop slowly around 1.5-1K for a second then drop to idle. I discintly remember before the RPMs would drop right to idle. My buddy said it could be due to my use of oiled air filters gunking up the MAP sensor or Idle control sensor/valve. Has anyone heard of this before?
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      01-03-2012, 04:21 PM   #2
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The M3 doesn't have a MAF sensor. It has a MAP sensor.
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      01-03-2012, 04:32 PM   #3
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Quote:
Originally Posted by Z K View Post
The M3 doesn't have a MAF sensor. It has a MAP sensor.
ok, would oil filters mess with a MAP sensor over time?
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      01-03-2012, 04:56 PM   #4
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No, MAP sensors are based on air pressure so it doesn't have an air flow reading element like a MAF. Oil can coat the MAP and it wouldn't make any difference.

I don't know about the Idle control sensor though or if that can be affected.
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      01-03-2012, 04:57 PM   #5
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please read OP's?

Quote:
Originally Posted by Z K View Post
The M3 doesn't have a MAF sensor. It has a MAP sensor.
He stated MAP, not MAF
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      01-03-2012, 05:07 PM   #6
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Quote:
Originally Posted by sbm3 View Post
He stated MAP, not MAF
Read the title of this thread and he edited his post to say "MAP" after I responded.
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      01-03-2012, 05:44 PM   #7
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Quote:
Originally Posted by FifthStreetz View Post
ok, would oil filters mess with a MAP sensor over time?
A filter would have to literally dripping wet with oil for this to happen.

As long as proper cleaning/reoiling procedures are followed - this will never be an issue.
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      01-03-2012, 05:51 PM   #8
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OOPS saw he meant Map. I'll leave the link up anyways.



Here is what K&N has to say about oiled filters and maf sensors.

http://www.knfilters.com/maf/massair.htm
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      01-03-2012, 06:27 PM   #9
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Quote:
Originally Posted by VSmotorsports View Post
Here is what K&N has to say about oiled filters and maf sensors.

http://www.knfilters.com/maf/massair.htm
K&N has a vested interest in selling oiled filters... I know from personal experience that it definitely does have an effect on MAF sensors.

I've had K&N oil destroy 2 MAF sensors on a previous car. They ran fine prior to changing the filter. After install of the K&N and driving on it a while, the car started running very bad. Hesitation on throttle and low boost. Diagnosed as a bad MAF sensor. After taking the sensor out, you can see the intake tract and sensor covered in oily residue from the K&N. Put in a new MAF and it was fine for a couple of months then it happened again. Installed another MAF, ditched the K&N and never had a problem after that. I'll never run an oiled filter on a MAF equipped car again.
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      01-04-2012, 01:02 AM   #10
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If thats not the issue, then does anyone know why my revs linger around 1.5K-1K when i lightly rev it in neutral?
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      01-04-2012, 07:56 AM   #11
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Quote:
Originally Posted by Z K View Post
K&N has a vested interest in selling oiled filters... I know from personal experience that it definitely does have an effect on MAF sensors.

I've had K&N oil destroy 2 MAF sensors on a previous car. They ran fine prior to changing the filter. After install of the K&N and driving on it a while, the car started running very bad. Hesitation on throttle and low boost. Diagnosed as a bad MAF sensor. After taking the sensor out, you can see the intake tract and sensor covered in oily residue from the K&N. Put in a new MAF and it was fine for a couple of months then it happened again. Installed another MAF, ditched the K&N and never had a problem after that. I'll never run an oiled filter on a MAF equipped car again.
This may also have to do with the proximity of the MAF sensor to the filter. I ran a K&N on my 2004 350Z for 14000 miles with no issue whatsoever, however the Z has a long intake tube and the MAF was around a bend in the tube so it may have been shielded from oil deposits. In any case, shouldn't be an issue in the M3.
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      01-04-2012, 12:32 PM   #12
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Quote:
Originally Posted by VVG View Post
This may also have to do with the proximity of the MAF sensor to the filter. I ran a K&N on my 2004 350Z for 14000 miles with no issue whatsoever, however the Z has a long intake tube and the MAF was around a bend in the tube so it may have been shielded from oil deposits. In any case, shouldn't be an issue in the M3.
I ran a K&N on my '03 350Z for over 50k miles and had no issues. One time, I even oiled it to the point where the filter oil pooled in the air box. Not the slightest hint of an issue.
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      01-04-2012, 01:18 PM   #13
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Quote:
Originally Posted by M3PO View Post
I ran a K&N on my '03 350Z for over 50k miles and had no issues. One time, I even oiled it to the point where the filter oil pooled in the air box. Not the slightest hint of an issue.
and I put a K&N in my 4-runner @ 38K miles. It has 161K on it now. No issues -
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      01-04-2012, 01:41 PM   #14
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There's different kinds of MAF sensors. I am referring to the hot wire MAF sensors from the mid to late 90s Nissans and Toyotas like the 300ZX, 240SX, Supra etc. On these cars, the air filter is mounted directly to the MAF sensor housing.



As mentioned before, the oil is not an issue with the MAP sensor on the M3.

Last edited by Z K; 01-04-2012 at 01:48 PM.
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      01-04-2012, 07:11 PM   #15
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I ran K&N on all my cars....not a single problem
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      01-05-2012, 12:06 PM   #16
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Oiled filters were notorious for ruining both MAF's on e39 m5's. $$$$$
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      01-05-2012, 12:49 PM   #17
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Quote:
Originally Posted by FifthStreetz View Post
does anyone know why my revs linger around 1.5K-1K when i lightly rev it in neutral?
I've read that due to emissions, but am not sure why. Also for engine not to stall from high revs. Or a combination of the 2 . I HATE rev-hanging too, so you're not alone. And there's nothing we can do without voiding the warranty, so I just live with it. Take care.
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