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Thread: Rough idle/misfire on startup, disappears after 1-2 minutes, any ideas?

  1. #1
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    Rough idle/misfire on startup, disappears after 1-2 minutes, any ideas?

    Hi,

    When I start the car (330i), it misfires and white/grey smoke coming out of the exhaust. After 1-2 minutes of idling or driving the problem disappears. No check engine light, only 1 stored code: Bank 2 Lean. I changed the sparkplugs, the whole CCV system with all the hoses, cleaned the throttle body, ICV, replaced fuel filter, checked intake hoses for cracks, couldn't find any. When I changed the CCV, cleaned the TB and ICV, the idle was good, no misfires just on the first start up after changing/cleaning them. After a few hours the problem came back. I checked my DISA, the seal is flat, the metal pin is ok, but on the other side, the plastic pin must we worn because I can move the flap a little (2-3 mm) and it doesn't closes as it should, I can rotate the flap 2-3 mm. The mechanism is working in the DISA (I covered the hole with my finger and it didn't let the flap close entirely, if I know right it means that it's working correctly).

    Can the DISA cause this? I haven't checked the injectors. Any ideas?

    Thanks
    Last edited by tomsh96; 06-17-2017 at 05:44 AM. Reason: Added plus information

  2. #2
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    No, the DISA won't cause the problem. A bad or failing DISA will only impact performance.

    How does the engine start? Does it start right up without any issues? Does the smoke have a sweet smell?

  3. #3
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    Starts with no problem, I know the coolant smell pretty good, because had a bad radiator, and the vents pushed it to the cabin before I did a cooling system overhaul, but the exhaust doesn't smell like that. The smell is neutral.

  4. #4
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    04 ZHP, 83 320i, 00 M5
    In regards to the smoke: http://procarmechanics.com/types-of-...-it-indicates/

    Have you cleaned the maf with maf cleaner?

  5. #5
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    I didn't clean it, but if I unplug it, nothing changes. Yesterday I started up the car, it began to misfire, shut down immediately and checked the spark plugs for any kind of fluid. The 3rd was wet a little bit, the others were dry. I checked the pistons, all looked the same with some black residue on them and if I'm correct it would be cleaner if it was a HG problem, so I the drips on the pistons was fuel. Should I clean the injectors?

  6. #6
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    EXOTICS
    Remove and check the rubber plugs at rear side of manifold (#15,#17):http://www.realoem.com/bmw/enUS/show...diagId=11_2879
    Inspect for cracks, clear codes.
    A jack of all trades, master of none.

  7. #7
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    These vacuum caps are in perfect condition. Is it normal if my expansion tank (didn't change it in time) blew 2 weeks ago, refilled the whole system with coolant/water and in 200km I had to top it up by 0.9-1 liter? Can be that much air in the system even if I bleed it?

  8. #8
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    1 Liter is ok, as long as it's not repeatedly required.
    Check fuel pressure at fuel rail,45~50psi.
    Clear codes, then rescan after a drive cycle.
    A jack of all trades, master of none.

  9. #9
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    I'm taking the car to the mechanic in 4 days. I'll update once it's done. Thanks!

  10. #10
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    The engine computer (DME) is running the engine in the open loop mode during the first minute or so. Open loop means that the DME ignores the data from the pre-cat O2 sensors, and uses an overly rich fuel/air mixture. The secondary air pump (SAP) runs during this time. Open loop is used to get the cats up to operating temperature quickly. The SAP injects air into the exhaust manifold to ensure the overly rich fuel/air mixture is fully burned. Disconnecting the MAF connector forces the DME to go into the open loop mode with the exception that the DME uses the pre-cat sensor data to determine the if the engine is running lean or rich.

  11. #11
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    So you say it could be the MAF? The only thing that I don't understand is why the misfire disappears?! Same thing if I restart the car immediately after the first start.

  12. #12
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    No, it's not the MAF as the engine runs fine once it goes into the closed loop mode. So, the MAF is fine. Something else is the cause. Does the engine suddenly (over a period of a few seconds) idle properly? This would indicate that the culprit is a part that is either used only during open loop operations OR something that changes mode when the engine goes into close loop ops.

    any changes in sound when the engine starts behaving properly?

  13. #13
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    Update: Blown head gasket, cracked head and engine block (Cylinder 3) . I have no idea, how this could happen since the engine haven't overheated once since I'm owning the car...

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