Shut down during breaking?

Discussion in 'Modifications And Maintenance' started by minnesotanice, Mar 10, 2023.

  1. minnesotanice
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    minnesotanice Well-Known Member

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    I was talking to a coworker who has a 2012 Forester (unknown trim) and he mentioned that the engine is shutting down while he is breaking at slower speeds. My initial thought is an O2 sensor might be going bad and throwing the car into self-preservation and shutting off.

    Any thoughts on what it could be? He plans on bringing it in to South St. Paul to get it checked out, but I thought I would reach out here first.
     
  2. Krazylegz1485
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    Krazylegz1485 Well-Known Member

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    Not pushing the clutch in? Haha.

    Does it idle fine otherwise? If it's an automatic perhaps maybe something with the torque converter not releasing properly/fast enough or something causing it to pull the motor down with it?
     
  3. minnesotanice
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    minnesotanice Well-Known Member

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    It is an automatic. He did have the transmission replaced by White Bear Subaru not long ago but they put a used one in.
     
  4. tangledupinblu
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    tangledupinblu Event Coordinator Staff Member

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    Hmmmm. Has he thought about taking it to them to diagnose?
     
  5. minnesotanice
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    minnesotanice Well-Known Member

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    He wasn't on planning on going back to White Bear, but he wasn't too keen as they were at fault for the transmission replacement in the first place. Not sure what they gave him as a warranty on the replacement.
     
  6. euro
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    euro Well-Known Member

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    sounds like he should bring it to White bear anyways if there's a paper trail of faulty work.
     
  7. Krazylegz1485
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    Krazylegz1485 Well-Known Member

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    I googled "Subaru Forester shuts off while braking" and this is the first thing I see.

    Screenshot_20230310-092535.png
     
  8. Chux
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    Chux Well-Known Member

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    I don't think it's even possible that it could be an O2/AF sensor


    Does it stall at the moment the car stops? I've had several that had torque converters that would stick locked, and kill the engine when stopping just like leaving the clutch engaged.

    Or does it just stall as the rpms drop after releasing the throttle? Several things that can cause trouble idling. Generally a sticking IAC valve or vacuum leak. This can usually be replicated by a free rev in park, it won't catch the falling rpms fast enough. Battery and alternator should also be tested, all grounds and battery contacts inspected, etc.
     
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  9. minnesotanice
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    minnesotanice Well-Known Member

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    I ask him more info on it, but sounds like we have a good starting point. I'll ask him to free rev it and check it. Thanks everyone!
     
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  10. Chux
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    Chux Well-Known Member

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    Also should check for trouble codes
     
  11. WRX1
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    WRX1 _ Staff Member

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    My initial guess is a transmission problem. Probably SUPER low on fluid and the converter doesn't unlock to freewheel.

    Does the car chug when it dies (like if you didn't push in the clutch), or is it a clean cutout? New problem since the trans swap? Once it dies, can you just crank it over and it just fires up?

    I would also check the oil level and the look/smell of the dipstick. Just to make sure that they were actually dumping the trans fluid into the trans and not the motor. You can also check the trans level, but you want everything up to operating temp before you check the level.
     
  12. minnesotanice
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    minnesotanice Well-Known Member

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    He brought it into the dealer and they found his drain plug had wiggled loose, didn't find out how low it was, but my guess is that would be the problem.

    I talked to him a bit more on Friday evening and he said that its a new problem since the trans swap (25k-ish miles) and that it would only occur at full stops, rolling stops were fine. Not sure if its a clean cut out but he did say he will have a rough idle from time to time.
     
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  13. Krazylegz1485
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    Krazylegz1485 Well-Known Member

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    Damn. That smells like some warranty work, as well as burnt tranny fluid.
     
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  14. JasonoJordan
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    JasonoJordan Well-Known Member

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    Wonder how much premature wear that transmission suffered. drain plugs that are torqued correctly won't wiggle loose....just saying.
     
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  15. Chux
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    Chux Well-Known Member

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    Sounds like the torque converter wasn't unlocking. Could just be from the low fluid level.
     
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  16. minnesotanice
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    minnesotanice Well-Known Member

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    Haven't talked to him since, but my hope is that it was just from low fluid level. He ended up disregarding the suggestion to bring it to White Bear and just went to Walser in South St. Paul, so hopefully it was just the fluid level, but hopefully no major damage to the transmission.
     
  17. Nhibbs
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    Nhibbs Well-Known Member

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    yikes that sucks. Sounds like the shop fudged up, hope they make it right.

    Just reading the first post symptoms it sounded kind of like what would happen to my old G35 when the crank position sensor was going bad. Would just die randomly when slowing down to a stop and would have a long crank before starting up too.
     
  18. Vector
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    Vector Rally Organizer

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    Ahh, the VQ35. Wonderful engine when it runs, but they'll drive you to alcoholism when some random sensor craos out and entirety separate systems start crapping out.
     
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  19. Nhibbs
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    Nhibbs Well-Known Member

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    Luckily the crank position sensor was super easy to replace. I think I was able to get to it without even jacking the car up.