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Thread: P0174 p1083 p1344 p1348

  1. #1
    Join Date
    Mar 2019
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    Georgia
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    325Ci

    P0174 p1083 p1344 p1348

    Hey guys,

    I’ve got the codes listed in the Title, P0174, P1083, P1344, and P1348. These are system too lean, fuel mixture too lean bank 2 sensor 1, and two cylinder misfires. If i am to unplug the MAF sensor, all codes go away except obviously MAF low input code, and the car drives smooth after idle. With MAF plugged in, i get really rough idle and misfires along with backfiring in intake. It’s definitely not the MAF because it is brand new. With that being said, with these codes i know there is probably a vacuum leak, i would just like to be pointed in some right directions as opposed to just taking stuff apart randomly. Here’s a list of what’s been done already that would have bearing on vacuum: New intake manifold gasket, New intake boots & New CCV system.

    Any help is appreciated!

  2. #2
    Join Date
    Jul 2011
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    2018 BMW M240i
    You likely have several vacuum leaks. So I’d have the intake manifold smoke tested and the leaks fixed first. Then I’d clear the codes and see what codes back.

    Misfires can be caused by a myriad of things:
    - bad spark plug
    - bad boot from the coil to the plug
    - bad coil
    - bad coil electrical connector
    - bad injector
    - burned valve
    - bad head gasket
    - $$$$.

    So smoke test first before nothing else.

    Btw, unplugging the MAF causes the engine computer (DME in BMWspeak) to run an overly rich fuel/air mixture. This masks the vacuum leaks. Vacuum leaks are technically unmetered air as the air hasn’t been measured by the MAF.
    Last edited by MarcoZandrini; 04-14-2019 at 07:46 AM.

  3. #3
    Join Date
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    Awesome will do thanks! And shouldn’t the misfires be connected to the vacuum though since they go away when MAF is unplugged?

  4. #4
    Join Date
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    They can be but it’ll take a pretty big vacuum leak to cause misfires. Smoke test first. Then correct the leaks and clear the codes. Drive the car and see what codes, if any, come back.

  5. #5
    Join Date
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    Update: still haven’t smoke tested (don’t have the machine) tried the old cigar trick and couldn’t tell much. Anyways i figured I’d see what i could see from usual suspects, and sure enough, the breather hose on CCV system was not on there good. Tried to wiggle it with manifold still on but couldn’t get it, so I Took manifold off and got the hose locked on. Buttoned back up, and wallah, codes and everything gone. There is still some hesitation though. Idle around 700 but rough, and when i press the accelerator the idle bogs first to about 400 RPM, then picks up fine. Any ideas as to what would cause that?

    *Taking car tomorrow to run smoke test*

    - - - Updated - - -

    Also forgot to mention, idle holds relatively steady except for intermittent intake backfires and it dips.

  6. #6
    Join Date
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    You need to rescan the computer for codes. You removed the intake manifold? You may have induced other vacuum leaks. You need to take the car to a reputable indie shop that specializes in bimmers for a smoke test. Try www.bimrs.org to find a shop near you.

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