it randomly surges while driving and goes very low but never stalls ?

2009 BMW 550I
119,000 MILES • V8 • 2WD • AUTOMATIC
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BHAMDOC1973
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It has an aftermarket air filter which i disconnected because it isn't connected right to the boot where the MAF sensor is. Cleaned MAF and the idle has gotten better, but it randomly surges while driving which affects how the car shifts. Also, if left parked Nd idling it would idle super for a while then all of a sudden surge and goes very low but never stalls then goes back to normal. It's the same car that has ABS codes which i cannot resolve. Changed the abs same thing. Battery is healthy. Charging system is above 14v.the idrive information system displays BMW logo but never gets to the main screen for nav/radio etc., just goes black the returns to BMW logo.
Feb 4, 2023 at 4:56 PM
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STRAILER
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I have seen the primary o2 sensor connectors get mixed up from side to side which causes this issue. Did you get a lean coded by chance and did this car had water damage? Also, what comes up in the CAN scan?

https://www.2carpros.com/articles/can-scan-controller-area-network-easy

It sounds like you have a Body gateway module that is going out, with the engine running tap on the module to see if things change. Here is the location so you can check it out. Check out the images (below). Please let us know what happens.
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Feb 5, 2023 at 11:16 AM
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BHAMDOC1973
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O2 wires are okay. No lean numbers, no other codes other than the IBS not recognized. I re-registered the battery, removed the oil level sensor and checked, same thing. Battery stays around 12 when off. Starts every time with no struggle. Ia scanner see that the voltage changes from 14.2 to 13.5-13-8 or so whenever the surge happens, definitely something electrical. Looked at module bumped it, but nothing changed, checked fuses in there all have power. No water or flooding signs anywhere.
Feb 5, 2023 at 2:57 PM
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BHAMDOC1973
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Some numbers.
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Feb 5, 2023 at 3:00 PM
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STRAILER
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Well, it looks like the radio has an internal fault. The fact that you cleaned the MAF sensor, and it got better is telling us the MAF is bad. I would get a new one because cleaning the sensor seldom works 100%. Also check for vacuum leaks.

Use this guide when the engine is cold only:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Check out the images (below). Please let us know what happens.
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Feb 6, 2023 at 12:55 PM
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BHAMDOC1973
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Tested the alternator and it was good. Is there an alternator relay? Sometimes the voltage jumps between 13.6 and 14.1 when the dips happen. No vacuum leaks i have tested for that. No thing happened when i hit the module.
Feb 8, 2023 at 7:22 AM
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STRAILER
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What about the MAF sensor?
Feb 9, 2023 at 10:44 AM
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BHAMDOC1973
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Just received a used air filter box to install it delete the aftermarket and it came with a MAF so i'll try it.
Feb 9, 2023 at 10:58 AM
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Sounds good let me know.
Feb 10, 2023 at 1:20 PM
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BHAMDOC1973
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The OEM used air box set up and mad did the trick most likely the MAF. Shifting is great and no more surging. Thanks
Feb 11, 2023 at 2:36 PM
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Yay! nice work glad we could fix it. Use 2CarPros anytime, we are here to help. Please tell a friend.
Feb 12, 2023 at 1:01 PM