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Old 06-14-2016, 10:52 AM   #1
1st Gear Newbie
Join Date: May 2016
Location: Toronto
Posts: 22
MAF Question

Hey Guys,

I recently bought an 02 bmw 320i used. The idle was a little rough so I changed the air filter and cleaner the MAF with a q-tip. Since Im an idiot, I broke one of the filaments on the MAF (ouch). I bought a replacement on ebay, installed it and now I am getting p0171 and p0174 codes. My scanner tells me at idle MAF is reading 3.5 g/s which is normal. I have just put in a new rad cleared codes and havent driven it really before this happen so it IS possible I had the p0171 and p0174 before. It is not idling rough and the acceleration seems fine but again I have not much to compare it too since I basically only drove it 3 min from where I bought it to my house. Can anyone give me some guidance on a way to diagnose if the MAF I bought is defective before I complain to the part supplier? Thanks in advance!
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Old 06-14-2016, 11:03 AM   #2
6th Gear Member
Join Date: Feb 2009
Location: Canada
Posts: 1,404
3.5 g/s is good, simply clear codes and drive it, see if it returns, go from there. Sometimes it isn't the MAF itself and rather the plug, inspect the wiring but if it's reading ok it is likely ok

If it still idles rough start with the very basics, do you have a crack/leak in the boots after the MAF?
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Old 06-14-2016, 11:15 AM   #3
1st Gear Newbie
Join Date: May 2016
Location: Toronto
Posts: 22
Maf Question

Im going to take it apart tonight and inspect all the intakes boots as I hear they are prone to cracking...thanks for the input
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Old 06-14-2016, 03:51 PM   #4
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Join Date: Jun 2007
Location: Ancaster
Posts: 3,570
You have a vacuum leak.

Dakar M3 Track Build Thread
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