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

Tiny
BHAMDOC1973
  • MEMBER
  • 2009 BMW 550I
  • V8
  • 2WD
  • AUTOMATIC
  • 119,000 MILES
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.
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Saturday, February 4th, 2023 AT 4:56 PM

10 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
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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Sunday, February 5th, 2023 AT 11:16 AM
Tiny
BHAMDOC1973
  • MEMBER
  • 1,656 POSTS
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.
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Sunday, February 5th, 2023 AT 2:57 PM
Tiny
BHAMDOC1973
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  • 1,656 POSTS
Some numbers.
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Sunday, February 5th, 2023 AT 3:00 PM
Tiny
KEN L
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  • 48,363 POSTS
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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Monday, February 6th, 2023 AT 12:55 PM
Tiny
BHAMDOC1973
  • MEMBER
  • 1,656 POSTS
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.
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Wednesday, February 8th, 2023 AT 7:22 AM
Tiny
KEN L
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What about the MAF sensor?
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Thursday, February 9th, 2023 AT 10:44 AM
Tiny
BHAMDOC1973
  • MEMBER
  • 1,656 POSTS
Just received a used air filter box to install it delete the aftermarket and it came with a MAF so i'll try it.
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Thursday, February 9th, 2023 AT 10:58 AM
Tiny
KEN L
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Sounds good let me know.
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Friday, February 10th, 2023 AT 1:20 PM
Tiny
BHAMDOC1973
  • MEMBER
  • 1,656 POSTS
The OEM used air box set up and mad did the trick most likely the MAF. Shifting is great and no more surging. Thanks
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Saturday, February 11th, 2023 AT 2:36 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
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Yay! Nice work glad we could fix it. Use 2CarPros anytime, we are here to help. Please tell a friend.
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Sunday, February 12th, 2023 AT 1:01 PM

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