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Steve
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Hi - Id like a second opinion. Car: E39 BMW(###) ###-####touring

Resolved Question:

Hi - I'd like a second opinion.
Car: E39 BMW(###) ###-####touring auto
History: 140000 miles - always serviced correctly - 2 thirds through current service interval
Fault: Engine starts and drives OK from cold, then after between 5 and 20 minutes driving - the engine goes faulty with:
low power at low rev range, engine note sounds a bit hollow, more difficult to restart with chugging/misfiring as it fires up.
It remains driveable, and reasonable power at higher revs.
The changeover point from OK to faulty running is very noticeable - if idling it will stop, if driving it will judder then continue.
If switched off for some hours it then starts and drives normally for first 5 - 20 mins again.
There have been no engine warnings or alerts on the dash.
An independent garage read the engine fault memory:
No DTC Description
1 BE Insufficient heat output, oxygen sensor behind catalytic convertor, bank 1
2 12 Signal, camshaft sensor, exhaust
3 41 Signal, inlet-camshaft sensor
4 53 Signal, crankshaft sensor
5 F4 Segment timing, true running disturbed
6 08 Signal, air-mass flow sensor
They said the problem was in the timing, requiring a rebuild with new timing chain and timing components, which would be uneconomical for the age and condition of the car. They simply read the existing codes and did not then clear the codes and read them again after driving with the fault, so I don't know which codes are related to the fault.
I would have expected failed timing components to cause consistently faulty running, and give an engine warning on the dash. The fact that it recovers overnight suggested that it might be something else.
Your thoughts please?
Thanks
Submitted: 2 years ago.
Category: BMW
Expert:  Steve replied 2 years ago.

hello

I will provide an honest answer. I trust this will be appreciated. Please remember that a low rating PUNISHES me for being honest and that I receive nothing for my time until a positive rating is clicked

I would not expect that the timing being off would casue an intermittent issue.

I would suspect possibly the airflow sensor as the culprit, or potentially a vanos issue.

as a next step, you could try drivinig with the airflow sensor unhooked.

I would also consider a software update at a bmw main dealer and potentially new cam and crank sensors as there have been some issues with them

I agree that a timinig job would not be a good investment given the value of the vehicle.

Please let me know if you have further questions. Please do not forget to click a positive rating as this is the only way I receive credit for my answer, thank you. Best wishes with your vehicle.

Customer: replied 2 years ago.

Thanks - I do have a couple of follow on questions.

Firstly, where do I find the airflow sensor, and how do I unhook it?
And if it is unhooked - what does this actually do for the engine?

Expert:  Steve replied 2 years ago.

Please do not forget to click a positive rating as this is the only way I receive credit for my answer, thank you.

the airlflow sensor is on the intake side of the engine near the air filter box per the images below. you simply disconnect the electrical connector. If you are not familiar with this type of thing then you should consider having a professional do it.

unhooking it makes the engine use default air/fuel mixture values. if the sensor is faulty, running with it unhooked will cause the issues to cease. You may also want to have the intake checked for leaks and the crankcase ventilation system tested, although these are less likely to cause what you have described.

http://klinquist.smugmug.com/photos/421026333_mVeYh-M.jpg

part #1 here: http://www.realoem.com/bmw/diagrams/u/x/114.png

Please do not forget to click a positive rating as this is the only way I receive credit for my answer, thank you.

Customer: replied 2 years ago.

Thanks very much for that.

The second question is what is the vanos?

If you could return some diagrams and images as well again, that would be helpful.

Expert:  Steve replied 2 years ago.

Please do not forget to click a positive rating as this is the only way I receive credit for my answer, thank you.

the vanos is a variable timing unit

it cannot be worked on at home, it 100% requires a professional and special tools

https://www.google.com/search?q=m54+vanos&client=firefox-a&hs=kqM&rls=org.mozilla:en-US:official&channel=np&tbm=isch&tbo=u&source=univ&sa=X&ei=nwH-U9LtBMqpyATq84DwBQ&ved=0CCgQsAQ&biw=1366&bih=657

http://en.wikipedia.org/wiki/VANOS

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Customer: replied 2 years ago.

Oh I see - so fixing vanos would be part of that prohibitively expensive timing repair job then.

I just read up about how the vanos seals failure can cause my symptoms. But again I would expect consistent problems now following a gradual deterioration in performance.

Do you think vanos is likely or unlikely in my case, given the overnight recovery, and the fact that no specifically vanos fault codes were there?

Expert:  Steve replied 2 years ago.

Please do not forget to click a positive rating as this is the only way I receive credit for my answer, thank you.

I think it is unlikely. as the question has been answered, please kindly CLICK ON a positive ratinig. thank you

Please do not forget to click a positive rating as this is the only way I receive credit for my answer, thank you.

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