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  #21  
Old 01-09-2024, 12:01 PM
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Quote:
Originally Posted by 80stech View Post
Any air not going through the MAF isn't measured.
Yeah I understand that. But if there is a vacuum leak after the maf(intake boots etc) why would the maf be reading lower? Wouldn't it be correct value then the vacuum leak would mess up that value later without the maf knowing.

What are the chances I was given a fake MAF or defective MAF?
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  #22  
Old 01-09-2024, 12:21 PM
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If the air is going around the MAF the MAF can't measure it. MAF stands for "Mass Airflow Sensor" and the big advantage of it is that it is a direct measurement of the volume and density of the air going through it, there is no speed/density calculation needed. ANY air leak (including engine block) that is after the MAF isn't measured and won't affect the reading unless the DME is ignoring the MAF. If something on the air filter side leaks then that doesn't affect the reading. That being said the only real way to rule out a MAF is to replace it with a known good unit. Did you check the vacuum caps at the back of the manifold ?? That would explain the problem being only on bank 2.
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  #23  
Old 01-09-2024, 01:23 PM
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Originally Posted by 80stech View Post
If the air is going around the MAF the MAF can't measure it. MAF stands for "Mass Airflow Sensor" and the big advantage of it is that it is a direct measurement of the volume and density of the air going through it, there is no speed/density calculation needed. ANY air leak (including engine block) that is after the MAF isn't measured and won't affect the reading unless the DME is ignoring the MAF. If something on the air filter side leaks then that doesn't affect the reading. That being said the only real way to rule out a MAF is to replace it with a known good unit. Did you check the vacuum caps at the back of the manifold ?? That would explain the problem being only on bank 2.

I did replace the MAF, but the reading was exact same. So I just returned it. My current MAF is a Siemens and the one I bought was a VDO so i assume it was OEM Quality.

I plan on looking at it this week, Its raining here so prob will wait till its nice out. Is there a diagram or video I could look at to help?
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  #24  
Old 01-09-2024, 01:40 PM
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My P1093 SES light was solved by changing the Post Cat Bank 2 Sensor 2 , car is now 186k and this was back in 2016....
that thread is on here if you searched hard enough...
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  #25  
Old 01-09-2024, 01:48 PM
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Originally Posted by docnabimmer View Post
My P1093 SES light was solved by changing the Post Cat Bank 2 Sensor 2 , car is now 186k and this was back in 2016....
that thread is on here if you searched hard enough...

I did find couple threads about Post Cat Bank 2 Sensor 2 being the fix, but I also saw people saying that replacing them didnt fix it either. If I would go down that route, whats the best way to get it out? I assume that since it gets very hot down there, trying to loosen it is gonna be a pain.
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  #26  
Old 01-09-2024, 02:18 PM
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Quote:
Originally Posted by Optllizer View Post
I did replace the MAF, but the reading was exact same. So I just returned it. My current MAF is a Siemens and the one I bought was a VDO so i assume it was OEM Quality.

I plan on looking at it this week, Its raining here so prob will wait till its nice out. Is there a diagram or video I could look at to help?

What 80stech means is that if there is a vacuum leak somewhere downstream of the MAF, if you replace the MAF the new one will still read the same, because you didn't fix the leak. (The leak is when the vacuum of the intake manifold sucks in air from the leak so it is not measured by the MAF, which means the proper amount of fuel is not injected.)



Your reading of 2.6 g/s is a little low but doesn't seem out of the ordinary. Mine read I think 3.3 g/s.
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  #27  
Old 01-09-2024, 02:19 PM
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contrary to some O2 sensors are maintenance items (see JFOJ E46fanatics) they dont last forever, i changed the Post Cat O2 from down below using ramps while doing an oil change...change them on a cold engine.
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  #28  
Old 01-09-2024, 03:50 PM
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Some good news, so one of the smaller vaccum hoes connecting to the lower intake boot wasnt in all the way. Its the bigger one so i think the brake booster? Anyway it was bit annoying but with some force, got it in. I had inpa opened to see if it made any difference. I also tightened the lower intake boot. Bank 2 dropped from 20 to 10 then with the brake booster hoses dropped to 3-4 which was in green range. Probably still have a tiny vaccum leak somewhere but no codes just gonna let it go. ill see if p0174 comes back. MAF is also now reading 3.6 so thats good.

P1093 is next, will prob replace the post cat sensor soon.

Thank you for dealing with me ��. Sometimes have hard time understanding some stuff so extra explanations are great.
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  #29  
Old 01-09-2024, 03:54 PM
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Wow! Lucky! Seems like it takes months and months for most people to chase the P0174 codes around here! Well, report back if you find any more. I think P0174s are one of the trickier problems with M54s and that we will be seeing more and more members with problems.
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  #30  
Old 01-09-2024, 04:02 PM
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Originally Posted by Bdc101 View Post
Wow! Lucky! Seems like it takes months and months for most people to chase the P0174 codes around here! Well, report back if you find any more. I think P0174s are one of the trickier problems with M54s and that we will be seeing more and more members with problems.
Im still not 100%, gotta go through more drive cycles. But trims and maf are readings seem good at warm idle. But im confident.
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