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2003 E46 325
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Discussion Starter #1
2003 325i m54
So while doing some research on MAF sensors I learned about STFT So I noticed that Mine was out of place running normally in the 20's while my LTFT was reading 0's when you step on the accelerator to about 2500 rpm that number comes down. between 7-10 g/s. I read where this could be one of three things
1.Vaccuum leak
2. MAF Sensor
3. o2 sensors

Well I actually have a MAF on order just because I'm not sure if it has ever been changed.
Vaccuum leak. I have replaced most and smoke tested for vaccumm leaks I know that i have a bad brake booster. So I unplugged the hose from the brake booster and plugged it for testing purposes. No difference noted.
I took a picture of the lambda probe and the fuel adaptations. Please let me know what you think
on the bottom 2 that are maxed out at 99.31 when i first started the car they were actually reading what seemed like normal numbers then they switched to these numbers.
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If O2 sensors were disconnected I believe DME would use a default substitute value of 0.45V. Constant low voltages on all 4 sensors tell it's running lean because it's very unlikely all the sensors would fail in the same way at the same time. Also if front two sensors were disconnected the lambda integrator values should default to 0%. The heating values are fine. They tell all four O2 sensors are on operating temperature. At cold start it's normal for these numbers to be low and rise to 99.x% as O2 sensors warm up.

Since you say values get better with raise RPM vacuum leak would be primary suspect. Bad MAF's would typically show worse values with higher RPM.
 

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2003 E46 325
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Discussion Starter #4
Update New MAF came in today so after putting it on I noticed a difference each pic is one at idle and one at 2k while driving with a cheapo obd my stft at the highest was between 0-10 +- but definitely a big difference from just being pegged out to 28 all the time.
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2003 E46 325
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Discussion Starter #8
I would agree with loty1825 that it is most likely a vacuum leak.
How many miles on the car? O2 sensors?
What brand MAF did you buy?
196k on the miles maf sensor was a vdo/siemens I did find my vacuum leak. it is my disa valve mounting o ring. I found it by spraying some carb cleaner on it and watched my stft drop down into range . so part was the MAF and part was the vacuum leak.

Bali dawg- I agree with you I will probably change it soon.
 
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