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General E46 Forum
This is the place to get answers, opinions and everything you need related to your E46 (sedan, coupe, convertible and wagon) BMW!

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Old 12-07-2016, 12:33 PM   #1
B694515
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Check engine light will not go away even after O2 sensor replace. Should I do this?

In addition to my suspension/wheel upgrade, I need to address why my check engine light keeps coming on even after I replaced both pre-cat O2 sensors. I have had this problem since 2012. I made a few posts regarding it in the past but I was never able to figure it out. I took it to BMW and they said replace the pre-cat O2 sensors because I was getting lean codes. I bought the parts and did it myself and I thought that fixed it but whenever I gun the car, the light will come on and won't go away till I erase it.

I took it to my local mechanic who works on BMW's and he said to replace the intake manifold gasket and while he does that he will replace the CCV. He said that will definitely take care of it. He also quoted $1000 for the job.

Should I do this? We don't know for a fact what is causing the CEL but my research tells me this is a vacuum leak and replacing the CCV and intake manifold gasket should ideally address this problem. I just don't want to do it if it's not warranted and if I do choose to do it, is there anything else that needs to be changed while he's working in that area? I watched a video and that looks like a pretty intricate job.

Thanks
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Old 12-07-2016, 12:42 PM   #2
All2kool
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For accurate help, post the codes.
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Old 12-07-2016, 12:47 PM   #3
jfoj
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Lean codes are not caused by bad O2 sensors. A bad O2 sensonr cannot properly detect a Rich or Lean condition.

If you car has Lean codes, need the codes and Freeze Frame data. The intake gaskets rarely leak and the intake does not need to come off for the CCV to be replaced.

Before you do anything, we need data. If you do not have an OBDII tools, bet the OBDFusion App and VeePeak interface from Amazon, all less than $30.
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Solve your misfires, lean codes, rough idle - http://forum.e46fanatics.com/showthread.php?t=897616

Fuel pump failures - http://forum.e46fanatics.com/showthread.php?t=929501

Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temp, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

E46/E39 GM5 Door Lock Info - www.bmwgm5.com

Lower hose temp switch O-ring - BMW #13621743299
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Old 12-07-2016, 01:18 PM   #4
Landlorder
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Intake manifold gasket and ccv pipes cost about $180 max? $800 plus labour is ridiculous. It's a 6 hour diy job easy.
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Old 12-07-2016, 01:20 PM   #5
RayPooley
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Quote:
Originally Posted by B694515 View Post
In addition to my suspension/wheel upgrade, I need to address why my check engine light keeps coming on even after I replaced both pre-cat O2 sensors. I have had this problem since 2012. I made a few posts regarding it in the past but I was never able to figure it out. I took it to BMW and they said replace the pre-cat O2 sensors because I was getting lean codes. I bought the parts and did it myself and I thought that fixed it but whenever I gun the car, the light will come on and won't go away till I erase it.

I took it to my local mechanic who works on BMW's and he said to replace the intake manifold gasket and while he does that he will replace the CCV. He said that will definitely take care of it. He also quoted $1000 for the job.

Should I do this? We don't know for a fact what is causing the CEL but my research tells me this is a vacuum leak and replacing the CCV and intake manifold gasket should ideally address this problem. I just don't want to do it if it's not warranted and if I do choose to do it, is there anything else that needs to be changed while he's working in that area? I watched a video and that looks like a pretty intricate job.

Thanks
Post your codes. If you don't have a code reader buy one. You don't have to have an all bells and whistles, super duper, cure all code reader. Just a hand held one. Spending $50 on a hand held code reader is a far better investment than paying it to a mechanic to fiddle with your car for half an hour. So find out what codes you are getting, rule out the unlikely causes and narrow it down to what it is most likely to be. Note that lean codes can have many causes, even a combination of causes, so check out jfoj's comprehensive write up. But I wouldn't just take the diagnosis of a grease monkey for gospel and especially not a dealership when it comes to diagnosis. $1000 is a lot of wedge. Not for an intake manifold and ccv replacement if you actually need it but chances are you don't. Read fjoj's stuff before you go handing over that kind of readies.
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Old 12-08-2016, 12:36 AM   #6
Kpriest
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Quote:
Originally Posted by B694515 View Post
In addition to my suspension/wheel upgrade, I need to address why my check engine light keeps coming on even after I replaced both pre-cat O2 sensors. I have had this problem since 2012. I made a few posts regarding it in the past but I was never able to figure it out. I took it to BMW and they said replace the pre-cat O2 sensors because I was getting lean codes. I bought the parts and did it myself and I thought that fixed it but whenever I gun the car, the light will come on and won't go away till I erase it.



I took it to my local mechanic who works on BMW's and he said to replace the intake manifold gasket and while he does that he will replace the CCV. He said that will definitely take care of it. He also quoted $1000 for the job.



Should I do this? We don't know for a fact what is causing the CEL but my research tells me this is a vacuum leak and replacing the CCV and intake manifold gasket should ideally address this problem. I just don't want to do it if it's not warranted and if I do choose to do it, is there anything else that needs to be changed while he's working in that area? I watched a video and that looks like a pretty intricate job.



Thanks

I have had a similar issue. I will occasionally get a P0171 and P0174 and when I check the freeze frame data it is at around 2000 rpm when the car is moving. I am certain it is a vacuum leak on my car, I just ordered parts to redo the CCV system and I am removing the intake manifold to do it. Just to make things more accessible and the peace of mind to replace that intake manifold gasket at the same time as the CCV system. While I'm in there I'm going to replace the vacuum lines that are under the manifold and behind as well as the intake boots. In addition I am rebuilding my DISA with a new flap and O-ring along with a new brake booster vacuum like because my original one is as hard as a rock.

Parts for this job
$162 for CCV kit, Genuine BMW brake booster hose, Intake Manifold gasket from FCP Euro
$78 DISA rebuild kit from German Auto Solutions

For $240 I am able to replace most of the small points of failure to cause a vacuum leak in addition to just the CCV. If you have a good set of tools and a weekend to put toward the job I wouldn't pay a mechanic to do the job.
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Old 12-08-2016, 08:13 AM   #7
jfoj
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Quote:
Originally Posted by Kpriest View Post
I have had a similar issue. I will occasionally get a P0171 and P0174 and when I check the freeze frame data it is at around 2000 rpm when the car is moving. I am certain it is a vacuum leak on my car, I just ordered parts to redo the CCV system and I am removing the intake manifold to do it.
I can almost guarantee that a Lean code at 2000 RPM is not a vacuum leak, but a MAF and/or fuel supply problem, most likely a soft fuel pump.

While the car WILL need the CCV and hoses replaced, I would not expect this to solve a 2000 RPM Lean condition.
__________________
Solve your misfires, lean codes, rough idle - http://forum.e46fanatics.com/showthread.php?t=897616

Fuel pump failures - http://forum.e46fanatics.com/showthread.php?t=929501

Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temp, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

E46/E39 GM5 Door Lock Info - www.bmwgm5.com

Lower hose temp switch O-ring - BMW #13621743299

Last edited by jfoj; 12-08-2016 at 08:14 AM.
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Old 12-08-2016, 09:12 AM   #8
Kpriest
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Quote:
Originally Posted by jfoj View Post
I can almost guarantee that a Lean code at 2000 RPM is not a vacuum leak, but a MAF and/or fuel supply problem, most likely a soft fuel pump.

While the car WILL need the CCV and hoses replaced, I would not expect this to solve a 2000 RPM Lean condition.

If it were a soft/failing fuel pump what other symptoms would there be? The fuel pump is original and the car has 95k miles on it. The fuel filter is less than 6 months old, I did that over the summer.
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Old 12-08-2016, 10:57 AM   #9
jfoj
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I will forgo a fuel filter on an E46 and replace the fuel pump first!

The E46 fuel filter is HUGE and BMW has a 90k mile Service Interval on the fuel filter.

My take is EVERY E46 needs a replacement fuel pump at this point in time. The fuel pump is much cheaper than the MAF and if the fuel pump solves your problem, you are done. If the fuel pump does not solve your problem, you then replace the MAF and at least you took car of one common failure point that will leave you stranded by replacing the fuel pump. A bad MAF will almost never leave you stranded, but a bad fuel pump WILL.

As for other symptoms, I will let you hear directly from the end users, read - http://forum.e46fanatics.com/showthread.php?t=929501
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Solve your misfires, lean codes, rough idle - http://forum.e46fanatics.com/showthread.php?t=897616

Fuel pump failures - http://forum.e46fanatics.com/showthread.php?t=929501

Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temp, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

E46/E39 GM5 Door Lock Info - www.bmwgm5.com

Lower hose temp switch O-ring - BMW #13621743299
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