Fiesta cutting out when braking hard.

  1. zardoz

    zardoz Old school Socialist

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    Chetser, UK
    I bought an 04 petrol fiesta 1300 7 month ago. From the get go it cut out when braking hard or even not so hard. It was such a good car in every other respect that i thought, what the hell Ill just keep it and fix it, in the meantime not stamping on the brakes.

    Well i looked it up and got all sorts of answers, fuel sensor, fuel filter, idle speed control valve, lambda sensors, etc. One of the weirdest but simplest 'fixes' was to disconnect the battery for 20 minutes. So i tried that first and hey presto it worked. ! well for all of 4 months now its back again. So i have turned to the most knowledgeable people i know. ie: this forum.

    Any one here able to help ?

    ps happy holidays
     
    Last edited: Dec 26, 2016
  2. zardoz

    zardoz Old school Socialist

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    Good question, will try in the morning.
     
  3. The_Yellow_Ardvark

    The_Yellow_Ardvark perkele

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    @zardoz
    Check/replace the hose from the brake servo to the fuel system.
    Mother in law Fiesta had the same problem.
    Turns out when heavy breaking the servo allowed the inlet vacuum to leak out, weakling the mix to the point the engine would cut out.
     
  4. Robotstar5

    Robotstar5 Casanunda Staff Member

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    I had a Mini where the engine would rock forward under engine braking and short the main battery cable against the hot exhaust.
     
  5. Vacuum leak on manifold somewhere
     
  6. Badger1bear

    Badger1bear If your not on fire, then your too far away

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    kent
    Keep it simple

    Check earth straps

    Thank me later
     
    doubleboost likes this.
  7. Justme

    Justme Member

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  8. I have developed a habit when I want to acknowledge people following me (like a thank you for letting me pull out etc) to dab the brake pedal to flash the rear brake lights but on the VW T5 the engine cuts out momentarily. Perhaps the Fiesta has a similar setup and the throttle is adjusted too high? Just a stab in the dark.
     
  9. Chop 13 Member

    Messages:
    10
    Location:
    Manchester
    My vectra was doing that turned out to be the crank sensor!!
     
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  10. the snooper

    the snooper getting older by the day

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    most people will think your just twitchy on the brakes :D I flash the hazards momentarily
     
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  11. Robotstar5

    Robotstar5 Casanunda Staff Member

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    If I saw that I would assume you were braking and start doing the same myself, I use a couple of flashes of the hazards instead.
     
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  12. dobbslc

    dobbslc Member

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    Yeah left right flick of the indicators for me.
     
  13. I don't jam on the brakes just tap two or three times in quick succession. Anyway, it's not about my habits, I'm just thinking the reason for the intermittent cutting out is the brake light circuit when on the accelerator may be causing it.
     
  14. Justme

    Justme Member

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    Modern cars cut the gas if you are braking.
    Some even give error codes if you have a foot on the gas & brake at the same time.
    Are you dipping the clutch at the same time?
     
  15. Robotstar5

    Robotstar5 Casanunda Staff Member

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    I found that after going through a ford in the Navara, tried applying the brakes to dry them and the engine lost power.
     
  16. zardoz

    zardoz Old school Socialist

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    Just tried it twice and didn't happen when i had the clutch in too. So unless its a massive coincidence it might be indicative of ......?
     
  17. waddycall

    waddycall Member

    Messages:
    1,143
    United Kingdom
    Would this mean it's more likely to be something shorting/disconnecting as the engine moves around as with the clutch in the engine won't move on the mounts so much?
     
  18. Aaron_ Member

    Messages:
    186
    Location:
    Middlesex
    Try this unplug the plug on the speedo bit on the gearbox if that fixes it you will need to remove the throttle position sensor elongate the holes and then refit can't remember what wires just you need to set it to 0.7v that should fix it
     
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  19. This is why I suggested it in case the same thing applies with the Ford as my T5. Forgetting my bad habits, the point is with a partial throttle and brake applied the engine hesitates and cuts momentarily.
     
    Aaron_ likes this.
  20. Can'tWeld can sort of weld

    I'm wondering about this. Never encountered it for myself, but I recall being told that old Fords had a crash sensor which was basically a tube with a ball bearing inside, under extreme deceleration the ball bearing would shoot forward and cut power to the fuel pump.

    Perhaps find out where it is and bypass it?

    Do modern cars even have that any more?
     
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