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Unread 07-05-2010, 01:33 PM   #1
BrandonRay
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MAF same as MAP sensor???

I used the search tool and checked my service manual but couldn't find anything. I threw a P0171 code... running lean on bank 1, so I wanted to clean the MAF sensor. Anyway I couldn't find it in the service manual index. All I found was a MAP (Maximum Absolute Pressure) sensor.

So I was wondering, is this just a new name for the Mass Air Flow sensor??? I have a 2005 LJ 4.0 I6.

Thanks

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Unread 07-05-2010, 01:49 PM   #2
tknarr
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No, Mass Airflow Sensor is usually found in the air intake system and measures airflow to the engine.
Manifold Absolute Pressure sensor is usually found in the intake manifold and measures vacuum? (anyone fell free to jump in here and correct me).
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Unread 07-05-2010, 03:34 PM   #3
BrandonRay
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Yeah Manifold Absolute Pressure not "Maximum"... sorry for the typo... anyway I can't find anything on the MAF in my service manual... I'd think that would be something worth listing in the index.. thank you for the input!
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Unread 07-05-2010, 03:37 PM   #4
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The MAP sensor works alongside the TPS to measure the amount of air coming into the engine, if I am not mistaken. It's a speed-density system, of sorts. No MAF sensor is needed.
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Unread 07-05-2010, 03:37 PM   #5
Sweeney
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Well, your Jeep doesn't have a MAF sensor.
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Unread 07-05-2010, 03:41 PM   #6
joshr1987
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Yeah, while they are not the same, the do serve the same purpose. You wouldnt have both...
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Unread 07-05-2010, 03:56 PM   #7
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Quote:
Originally Posted by joshr1987 View Post
Yeah, while they are not the same, the do serve the same purpose. You wouldnt have both...
Well, kind of...so, just for the sake of clarity:

MAF directly measures the mass of the air that is entering the engine, and the computer adds fuel accordingly.

MAP measures the pressure of the air that's in the manifold...i.e. air density...and correlates that value with the computer and the throttle position at the time, which allows the computer to know how much air is actually entering the manifold; the computer then adds fuel accordingly. It's sort of an extra step in the process, so to speak.

So yes, in that they both serve the purpose of measuring how much air goes through the manifold, they are very similar. However, it's not quite accurate to say that they serve the same purpose, as they are designed for totally different applications.
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Unread 07-05-2010, 04:08 PM   #8
BrandonRay
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Yeah it doesn't seem like I'd need both... so I guess I'll clean the MAP and hope the MIL stays off and the MPG's improve a little.
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Unread 07-05-2010, 04:16 PM   #9
BrandonRay
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This is a little of what I found..

The MAP sensor is used as an input to the Powertrain
Control Module (PCM). It contains a silicon
based sensing unit to provide data on the manifold
vacuum that draws the air/fuel mixture into the combustion
chamber. The PCM requires this information
to determine injector pulse width and spark advance.
When manifold absolute pressure (MAP) equals
Barometric pressure, the pulse width will be at maximum.
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Unread 07-05-2010, 06:00 PM   #10
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P0171 can also be caused by low fuel pressure, and at times by a vacuum leak. The Bank 1 lean condition is detected by the upstream Bank 1 O2 sensor, and all it's telling you is that for one reason or another, it thinks you have too much air and/or not enough fuel in the front half of the engine. The MAF sensor - in this case, not present - may or may not have anything to do with it.
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Unread 07-05-2010, 06:20 PM   #11
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Originally Posted by Sundowner View Post
P0171 can also be caused by low fuel pressure, and at times by a vacuum leak. The Bank 1 lean condition is detected by the upstream Bank 1 O2 sensor, and all it's telling you is that for one reason or another, it thinks you have too much air and/or not enough fuel in the front half of the engine. The MAF sensor - in this case, not present - may or may not have anything to do with it.
Yeah my basic plan is to clean the MAP sensor, then replace if that doesn't work, if I still have the issue move on to checking the vacuum and PCV hoses, then the fuel filter, and the fuel pressure. Let me know if that sounds like the right path to take... I'm just learning here.
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Unread 07-05-2010, 06:37 PM   #12
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No offense, but why are you going to spend money on a new sensor before you check things that will cost you nothing? Looking over the vacuum lines and checking your fuel filter and fuel pressure costs you exactly $0. I promise a new MAP sensor will cost more than that.
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Unread 07-05-2010, 07:01 PM   #13
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Hopefully that pic goes through... if it does is that not a MAF on the air intake tube between the air filter housing and the throttle body? You can see the MAP in the bottom of the pic next to the throttle body.
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Unread 07-05-2010, 07:05 PM   #14
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Quote:
Originally Posted by Sundowner View Post
No offense, but why are you going to spend money on a new sensor before you check things that will cost you nothing? Looking over the vacuum lines and checking your fuel filter and fuel pressure costs you exactly $0. I promise a new MAP sensor will cost more than that.
None taken... the MAP's just under $20, and I wasn't sure what a PIA it would be to find a leak somewhere else... I haven't done it before. I was just thinking systematically.
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Unread 07-05-2010, 07:05 PM   #15
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I don't see any picture, but I don't need to. You don't have one. Trust us.
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