128i idle/power surging, but smooth with AC on

texas128i · 09-09-2017, 12:46 AM

So twice, out of nowhere, my 2008 128i with 85k miles suddenly starts having a sporadic idle and when I give it gas it is also acting like it is missing or something. This was 2k apart between the incidences. First thing I did on the first issue was change the oil (I had just recently bought the car and was not sure about the oil in it, you know, thanks to the lack of a dipstick).

So when this happened, the first thing I think of to try to get it to improve is turn on the A/C and this DID WORK. It fixes the rough idle and acceleration and I got things home (was not far). I also hear a noise from the engine when acting up. Somewhat a sequel/whine I would say. I have a video and will see if I can post a link.

My first suspicion is something to do with the Vanos. Tomorrow I will check for any codes, but I don't see the indicator light light anything is wrong.

Edit: I had also cleaned both the vanos solenoids when I changed the oil as well. They seemed fine from a general inspection.
Edit 2: I drove the car 10 minutes later and no issues.

Thoughts? I suspect the Vanos system and wondering if it is the eccentric shaft sensor. Might need to get things tested.

Thanks.

Kev312 · 09-14-2017, 12:43 PM

Look at the plugs first. If the plugs and coils are fowled it will cause the car to hesitate. At 85k miles, do you have history of when a tune up was last done? You can easily pull a plug out to check it's condition. Mine did the same thing at about 65k miles.

Also, a squeal or whine on start up could be a pully or condenser bearing.

09-09-2017, 12:46 AM	#1
texas128i New Member 3 Rep 6 Posts Drives: Alpine White 128i Join Date: Apr 2017 Location: Austin iTrader: (0)	128i idle/power surging, but smooth with AC on So twice, out of nowhere, my 2008 128i with 85k miles suddenly starts having a sporadic idle and when I give it gas it is also acting like it is missing or something. This was 2k apart between the incidences. First thing I did on the first issue was change the oil (I had just recently bought the car and was not sure about the oil in it, you know, thanks to the lack of a dipstick). So when this happened, the first thing I think of to try to get it to improve is turn on the A/C and this DID WORK. It fixes the rough idle and acceleration and I got things home (was not far). I also hear a noise from the engine when acting up. Somewhat a sequel/whine I would say. I have a video and will see if I can post a link. My first suspicion is something to do with the Vanos. Tomorrow I will check for any codes, but I don't see the indicator light light anything is wrong. Edit: I had also cleaned both the vanos solenoids when I changed the oil as well. They seemed fine from a general inspection. Edit 2: I drove the car 10 minutes later and no issues. Thoughts? I suspect the Vanos system and wondering if it is the eccentric shaft sensor. Might need to get things tested. Thanks. __________________ 2008 BMW 128i Auto+Paddles, Sport Package, Nav Last edited by texas128i; 09-09-2017 at 08:20 AM..
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09-14-2017, 12:43 PM	#2
Kev312 Second Lieutenant 238 Rep 204 Posts Drives: 2012 BMW 320i Join Date: Sep 2017 Location: Midwest iTrader: (0)	Look at the plugs first. If the plugs and coils are fowled it will cause the car to hesitate. At 85k miles, do you have history of when a tune up was last done? You can easily pull a plug out to check it's condition. Mine did the same thing at about 65k miles. Also, a squeal or whine on start up could be a pully or condenser bearing.
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