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Thread: Billowing white smoke / rough idle

  1. #1
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    Billowing white smoke / rough idle

    It's a 98 740i that the last few times i drove it drove just fine with no issues. It then was parked and spent about 6 months in the back of my family's property. Now upon start up it smokes pretty bad and if reved a few times the smoke begins to billow out of the exhaust pipes. It also has a rough idle but no check engine light probably due to the battery being disconnected for months. The smoke is thick enough upon reving to create a smoke screen fit for a hollywood production, so I am shying away from thinking it's the osv again. I changed the osv about 10,000 miles ago but the car has also sat around off and on since i did that about 8 years ago.

    Thank you for reading and also for any possible solutions you may offer.

  2. #2
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    If it was outside it may just be moisture in the exhaust system. My E32 did the same prior to restoring it when it sat for quite some time outside. Does it smell sweet or anything? White smoke is usually headgasket failure but if the car sat, my money is on just moisture in the exhaust.
    Have a look at the oil and coolant and make sure they are what they are supposed to be, and not chocolate milk

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  3. #3
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    Quote Originally Posted by Leone Sentinel View Post
    It's a 98 740i that the last few times i drove it drove just fine with no issues. It then was parked and spent about 6 months in the back of my family's property. Now upon start up it smokes pretty bad and if reved a few times the smoke begins to billow out of the exhaust pipes. It also has a rough idle but no check engine light probably due to the battery being disconnected for months. The smoke is thick enough upon reving to create a smoke screen fit for a hollywood production, so I am shying away from thinking it's the osv again. I changed the osv about 10,000 miles ago but the car has also sat around off and on since i did that about 8 years ago.

    Thank you for reading and also for any possible solutions you may offer.
    Read error codes, could be CCV if OSV was changed.

  4. #4
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    Quote Originally Posted by georgebest View Post
    Read error codes, could be CCV if OSV was changed.
    No check engine light, no error codes. Is there any other way to tell if it is the ccv?

  5. #5
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    If it was either, the smoke would be blue and reek of burnt oil. Does it?

    Some severe cases will cause a suction sound when you pull the dipstick out while the engine is running. Not always though. Give it a try. Have you let it idle for more than 10 min? If it sat for that long. Let it idle and monitor the Temps. See if the smoke goes away.

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  6. #6
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    Quote Originally Posted by SergeBMW View Post
    If it was outside it may just be moisture in the exhaust system. My E32 did the same prior to restoring it when it sat for quite some time outside. Does it smell sweet or anything? White smoke is usually headgasket failure but if the car sat, my money is on just moisture in the exhaust.
    Have a look at the oil and coolant and make sure they are what they are supposed to be, and not chocolate milk

    Sent from my ONEPLUS A3000 using Tapatalk
    Quote Originally Posted by georgebest View Post
    Read error codes, could be CCV if OSV was changed.
    The smoke smells very heavily of exhaust and the oil looks good. At this point I am hoping it is water in the fuel system, the only thing is if that is the case I have no idea how long it will take for the exhaust to stop smoking.

    - - - Updated - - -

    Quote Originally Posted by SergeBMW View Post
    If it was outside it may just be moisture in the exhaust system. My E32 did the same prior to restoring it when it sat for quite some time outside. Does it smell sweet or anything? White smoke is usually headgasket failure but if the car sat, my money is on just moisture in the exhaust.
    Have a look at the oil and coolant and make sure they are what they are supposed to be, and not chocolate milk

    Sent from my ONEPLUS A3000 using Tapatalk
    Quote Originally Posted by SergeBMW View Post
    If it was either, the smoke would be blue and reek of burnt oil. Does it?

    Some severe cases will cause a suction sound when you pull the dipstick out while the engine is running. Not always though. Give it a try. Have you let it idle for more than 10 min? If it sat for that long. Let it idle and monitor the Temps. See if the smoke goes away.

    Sent from my ONEPLUS A3000 using Tapatalk
    It smells like exhaust and is white as can be

  7. #7
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    I would let it idle and drive it around the neighborhood if you can. If it was the osv or cyclone behind the timing chain it would be visibly blue and smell like burning oil. My E32 750 took maybe 20 min for the smoke to clear, and would come back for a few days on cold starts until it cleared. I would also get some fresh fuel in there too. Has the rough idle gone away?

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  8. #8
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    I had white smoke with failed CCV, but I agree with the logic that it should have been blueish

  9. #9
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    I have let it run for over an hour today so far and it is still running currently. Still has a rough idle and is still leaking smoke like a smoke machine from the tail pipes. A very small amount of smoke is coming from the engine towards the firewall on the passenger side. Still no check engine light.

  10. #10
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    Check to see if the plugs are fouled up. Also when you look at the plugs, look to see if oil is pooling up in the plug wells.

    BMW 7er Website www.7er.com
    1989 BMW 735i Schwarz (sadly, sold) // 1989 BMW 750iL Cirrusblau Metallic // 1998 BMW 740iL Oxfordgrün Metallic // 2000 M5 Carbon Schwarz ///

  11. #11
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    I ended up running it for 2 hours straight and just from idling and a couple mins of reving i burned a 1/4 tank of gas. I feel like that is a horrible gas consumption rate.
    Also I plan to check the plugs tomorrow when I have sun light again.

  12. #12
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    Plugs are fine. This time i managed to burn up a quarter of a tank in about an hour. Something is making it burn up an excessive amount of fuel while running very rich

  13. #13
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    That much smoke and fuel consumption could be a failed FPR - when the diaphragm gives up raw fuel gets straight into the manifold. So, check the vacuum pipe that runs from the PCV to the FPR for signs of fuel......

    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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  14. #14
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    Sounds like the PCV is bad or the seal to the manifold is bad. Mine had the exact symptoms you described and a new PCV with fresh silicone around the perimeter solved it 100%. I used an ebay special $40 knock-off part and I have no complaints so far.

  15. #15
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  16. #16
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    If the fuel consumption is that bad I'd advise against running it too much longer. You run the risk of washing off the oil film on the bore -> extraordinary amount of rejoicing . The 'new engine' kind.

    You did, of course, check coolant level and coolant/oil colour, I assume.

  17. #17
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    Been working so much lately I finally just made time yesterday to spend some time with the car again. I also worked up the courage to take it for a quick drive even on bad tags, as a result the engine light turned on and I am now showing error codes P1585 P0308. If pcv and osv are the same thing as I currently believe them to be, I changed that part about 10,000 miles ago

  18. #18
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    Quote Originally Posted by Leone Sentinel View Post
    Been working so much lately I finally just made time yesterday to spend some time with the car again. I also worked up the courage to take it for a quick drive even on bad tags, as a result the engine light turned on and I am now showing error codes P1585 P0308. If pcv and osv are the same thing as I currently believe them to be, I changed that part about 10,000 miles ago
    They are different:
    OSV: behind lower timing cover, you need to remove the whole front of the engine to replace it (20-30 hours job)
    CCV: behind the intake manifold, 30-60 minutes job

    You would know if you replaced OSV

  19. #19
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    Here you go:

    https://www.meeknet.co.uk/e31/BMW_M6...entilation.htm

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    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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  20. #20
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    After reading the info in the link, it was definitely the ccv that I changed. That was 10,000 miles and years ago, so i forget if there was a way to tell if the ccv has failed by just examining it after removing it. I would love to save the money if it is not the pcv again. I do remember having a blueish tint to the smoke right before i changed that part as it describes in the website linked by Timm, where as what I am currently dealing with is white as can be and I also believe it to be producing a much richer exhaust/fuel smell this time around.

  21. #21
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    Diagnostics is the easiest way:



    https://www.meeknet.co.uk/E38/Diagnostics.htm
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


    My BMW Repair YouTube Channel
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  22. #22
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    Was this resolved? Having the same issue after timing chain/guide replacement. It’s burning 1/8 of a tank just idling in the driveway while troubleshooting. No CEL. It’s driving me nuts. Replaced the fuel filter and regulator while waiting for a new one to show up tomorrow. Messed with every vacuum connection. Checked the regular vacuum line and it’s clear. Return line clear from the filter. It billows fuel.

  23. #23
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    Sorry to resurrect, but I was still having this issue. The car ended up breaking a connecting rod due to cylinder wash.

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