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2004 XS AT
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2007 Forester Sports XT 4EAT
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Forester - USDM
• 98-99 ► MAF
• 2000-2004 NA (nonturbo) ► MAP
• 2004 XT and all 2005+ ► MAF
No cleaning instructions in the Subaru technical service manual, just a replacement procedure. :confused:

We've never cleaned the MAP sensor in my son's '03 X & it's running a K&N air filter. :wink:

Bobby...


['07 FSXT MODding Journal] ['03 X MODding Journal]
 

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2012 XT Touring 4EAT
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Remove the sensor. Blast it good, both inside and out, with an aerosol can of brake cleaner. Re-install.

Your K&N filter is oiled, right? Go sparingly on the oil. If you put too much, it will coat your MAP or MAF with oil - not the best possible thing.
 

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2004 XS AT
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Discussion Starter #5
Remove the sensor. Blast it good, both inside and out, with an aerosol can of brake cleaner. Re-install.

Your K&N filter is oiled, right? Go sparingly on the oil. If you put too much, it will coat your MAP or MAF with oil - not the best possible thing.
That's kind of my problem. A typical MAF sensor is easy to spray--just aim at the dangling wires and let it dry. On the '04's MAP sensor, there is only a pin-hole size cylinder that feeds into the sensor, not a pass-thru sensor of the MAF sort. I'm hesitant to spray up into the sensor, because I'd never be able to dry it, and it's unlikely to air dry.

Anyone ever try it on this car? I'd replace it, but it isn't faulting, and it costs $100. I was just trying to do K&N-related maintenance but running up against a quirky design.
 

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2004 XS AT
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God is its gasket, Bobby. (I don't know. I took it off, expecting to find a gasket, as you would, but nada. I put it back on, and I haven't had any warning lights come on. Dunno. Maybe I'm just super good at screwing in screws. :wink2:)
 

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‘14 FXTT; '15 Legacy FB25
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Your Subie is naturally-aspirated, right? The MAP sensor is always under vacuum, except when the throttle is wide open, where it might read near atmospheric. There's nothing blowing past it, like a MAF sensor's element, so I'm not sure what you would need to clean. It's simply a nipple, diaphragm and pressure (vacuum) transducer. I don't see how oil would get into it, unless the vacuum line leading to it is downhill form the intake, near where the filter is, and residual oil might leak down the vacuum tube into the map sensor.

I would be concerned more with damaging the sensor by blasting solvents into the vacuum port. If your engine is running fine, I'd clean the electrical contacts with alcohol and apply a thin layer of dielectric grease and call it a day.

EDIT: looked at the diagram above and it looks like this thing attaches to the manifold, is that right? I'm not sure why it would have a nipple for a vacuum tube, if it's mounted directly to the manifold; however, since it appears to be top-mounted I'd say there's even less reason to pull it for cleaning. The engine will draw vacuum and tend to suck the oil AWAY from the sensor. There's a chance some fine mist downstream of the filter could be pulled into the sensor when you go from idle (high vacuum) to WOT (low vacuum), since the diaphragm will move slightly away from the engine and possibly draw in a little bit of mist. Gravity will tend to drain it back out, but it could gunk up, I guess.

I would visually inspect the sensor, using a flashlight. If all looks good, then I would call it good.
 

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God is its gasket, Bobby. (I don't know. I took it off, expecting to find a gasket, as you would, but nada. I put it back on, and I haven't had any warning lights come on. Dunno. Maybe I'm just super good at screwing in screws. :wink2:)
Diagram says to replace the o-ring. If there was no o-ring when you pulled it, then maybe it was recessed and you missed it or there wasn't one and you should get one.
 

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2004 XS AT
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Discussion Starter #10
Diagram says to replace the o-ring. If there was no o-ring when you pulled it, then maybe it was recessed and you missed it or there wasn't one and you should get one.
Oh, I was only going about this because my mechanic said to clean the MAF sensor because of my K&N, which is oiled. I don't think he recollected off the top of his head that I have an MAP, which doesn't get the same treatment. I have already returned the cleaner to AutoZone.

I will call Subaru to see if they have an o-ring in the parts department.

Thanks for your thorough reply.
 
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