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1999 e39 528i 2001 e46 325i
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154 Posts
Discussion Starter · #1 ·
So I've run into another little issue with my 2001 BMW 325i and the problems are starting to get real. I am currently getting codes for lean mixture (P0171 P0174 P1083 P0185) it's starting to really affect driving. At a stoplight I can feel my car and see it dipping a small amount (about 1-100 rpms) but it will keep itself alive. now when I put my car into park allot of the time what will happen is my rpms will start bobbing up and down allot (about 100-300 rpms) and make it sound like my cars gonna stall out. I recently put in a new mass airflow sensor in from fcpeuro and it was the cheapest one they offered but it was still supposed to work. It was a bremi part so the real question I'm asking is are these codes a result of me adding that new mass airflow sensor or would it be a cold air intake/vaccume leak. I've recently repaired the boots on the intake and I've fixed allot of vaccume leaks. I'm thinking with the combination of maf and Cai that after this many years I should replace the fuel pump?
 

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2000 E46 323i, 3.0L, 2.8L and 2.0L Z3's
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The best way to find vacuum leaks is to smoke test the engine.

If you have a scanner you can also do this test.
With a hot engine at idle, look at the 4 fuel trims, 2 short term and 2 long term. If any are >8%, then you likely have a vacuum leak. Rev the engine to 3,000 rpm for 30 seconds and watch the short term fuel trims. If they reduce significantly, might even go negative, then its confirmed that you have vacuum leaks to find.

If they don't reduce significantly, then you don't have vacuum leaks. Fault find the fuel system (50 PSI at the fuel rail) and the MAF.
 

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Registered
1999 e39 528i 2001 e46 325i
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154 Posts
Discussion Starter · #4 ·
The best way to find vacuum leaks is to smoke test the engine.

If you have a scanner you can also do this test.
With a hot engine at idle, look at the 4 fuel trims, 2 short term and 2 long term. If any are >8%, then you likely have a vacuum leak. Rev the engine to 3,000 rpm for 30 seconds and watch the short term fuel trims. If they reduce significantly, might even go negative, then its confirmed that you have vacuum leaks to find.

If they don't reduce significantly, then you don't have vacuum leaks. Fault find the fuel system (50 PSI at the fuel rail) and the MAF.
Would I be able to accomplish this with an FOXWELL NT301? I'm new to cars and this is my first one so I'm just unfamiliar with how I would do that with a code reader.
 

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1999 e39 528i 2001 e46 325i
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154 Posts
Discussion Starter · #5 ·
No sense even talking about it without providing the MAF value and fuel trims at hot idle.
Post that data and let’s see what’s up.
Will definitely get it up tomorrow I also emailed fcp and they're sending a new sensor because they said it's likely that it's defective
 

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Would I be able to accomplish this with an FOXWELL NT301?
If you have a smartphone or tablet, I would skip the handheld scanner and just get a wireless OBD adapter and the OBD Fusion app.
Way cheaper, better user interface, more features.
 

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1999 e39 528i 2001 e46 325i
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154 Posts
Discussion Starter · #7 ·
If you have a smartphone or tablet, I would skip the handheld scanner and just get a wireless OBD adapter and the OBD Fusion app.
Way cheaper, better user interface, more features.
Just ordered the veepeak BT LE thanks for that info ive always wanted to get Carly but never thought it was worth it. On the other hand, what can I do in the meantime? should I just wait for the replacement maf and if that doesn't work report back with the data?
 
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