Light throttle Rpm surging/ O2 sensors ?

Mkgschmidt · 10-16-2021, 05:26 PM

Hey guys I’m dealing with a very weird and annoying problem on my 2007 335i N54

I started to notice when cruising on the highway on a flat stretch with very light throttle input (less than 10%) my car would do a weird surging as if i’m hitting the throttle and letting off repeatedly. Now I figured out it also does this in park and more intensely. When I rev the car up in park to around 1500 rpm it will bounce quite wildly 150-200 rpm up and down surging and making gargling noises from the exhaust. This phenomenon was seemingly accompanied by a code For Fuel mixture control bank 1 lean , 29E0 I believe. I recently replaced my turbos about 9000km ago but it ran awesome for like 5000 before i started noticing this. I didn’t mix up the O 2 sensors already checked that. I went ahead and unplugged the 2 front O2 sensors and re tested by reving up to 1500 rpm and it mostly fixed the issue, still does the bounce but much much less, possibly just because the sensors are disconnected. My vacuum lines are all brand new, also have silicone inlets and upgraded new charge pipe. Any help would be greatly appreciated since this is making the car very annoying to drive.
Ps Also I reset my adaptation the other day and that fixed it for about a day until the issue came back

Mkgschmidt · 10-18-2021, 05:21 PM

anyone?

aidan3603 · 10-18-2021, 06:37 PM

Quote:

Originally Posted by Mkgschmidt

anyone?

same problem on the car i just bought

Mkgschmidt · 10-18-2021, 10:12 PM

I’m sort of thinking it could be O2 sensor related. When I unplug both front O2s which puts the car into open loop it actually runs fine. Also when i reset the O2 sensor adaptations it runs perfect again. Maybe one O2 sensor is given a wrong reading and it’s making it run unbalanced

10-16-2021, 05:26 PM	#1
Mkgschmidt Enlisted Member 8 Rep 47 Posts Drives: 2007 BMW 335i Join Date: Jul 2021 Location: Quesnel B.C, Canada iTrader: (0)	Light throttle Rpm surging/ O2 sensors ? Hey guys I’m dealing with a very weird and annoying problem on my 2007 335i N54 I started to notice when cruising on the highway on a flat stretch with very light throttle input (less than 10%) my car would do a weird surging as if i’m hitting the throttle and letting off repeatedly. Now I figured out it also does this in park and more intensely. When I rev the car up in park to around 1500 rpm it will bounce quite wildly 150-200 rpm up and down surging and making gargling noises from the exhaust. This phenomenon was seemingly accompanied by a code For Fuel mixture control bank 1 lean , 29E0 I believe. I recently replaced my turbos about 9000km ago but it ran awesome for like 5000 before i started noticing this. I didn’t mix up the O 2 sensors already checked that. I went ahead and unplugged the 2 front O2 sensors and re tested by reving up to 1500 rpm and it mostly fixed the issue, still does the bounce but much much less, possibly just because the sensors are disconnected. My vacuum lines are all brand new, also have silicone inlets and upgraded new charge pipe. Any help would be greatly appreciated since this is making the car very annoying to drive. Ps Also I reset my adaptation the other day and that fixed it for about a day until the issue came back
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10-18-2021, 05:21 PM	#2
Mkgschmidt Enlisted Member 8 Rep 47 Posts Drives: 2007 BMW 335i Join Date: Jul 2021 Location: Quesnel B.C, Canada iTrader: (0)	anyone?
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10-18-2021, 10:12 PM	#4
Mkgschmidt Enlisted Member 8 Rep 47 Posts Drives: 2007 BMW 335i Join Date: Jul 2021 Location: Quesnel B.C, Canada iTrader: (0)	I’m sort of thinking it could be O2 sensor related. When I unplug both front O2s which puts the car into open loop it actually runs fine. Also when i reset the O2 sensor adaptations it runs perfect again. Maybe one O2 sensor is given a wrong reading and it’s making it run unbalanced
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