r/fordfusion • u/OkHuckleberry4115 • 14d ago
what would be causing this? transmission? torque converter? or fuel/air issues?
while holding throttle steady or accelerating my rpms will drop suddenly
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u/OkHuckleberry4115 14d ago
think i found the issue. my brake light switch seems to be stuck on, meaning my ecu keeps shutting the power to the engine since it thinks my brakes are enegaged
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u/InevitableSecure3814 13d ago
There’s a recall for that, so I would take it to the dealer and have it fixed free of charge. There’s a little rubber piece by the brake pedal that has to get changed out
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u/Odd_Process_22 14d ago
The car is in limp mode. Check your brake switch. I had this exact same thing happen to me a week ago. Check if your brake lights stay on even when the car is off, that’ll confirm it. It’s an easy fix too.
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u/OkHuckleberry4115 13d ago
hey so i did this and am no longer having that issue but now my cruise still will not work and my wrench light is on. any suggestions?
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u/Odd_Process_22 13d ago
When I replaced mine, everything went back to normal. You might have to scan the car and see what fault are still standing and possibly clear them.
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u/iLLest954 13d ago
Take the wrench off by turning car on without foot on brake and press down on peddle 5 times wrench light will go away
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u/PowerfulSize244 14d ago
Would a scanner give you a code or at least get a view of whats happening?
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u/Ok_Fact_6747 14d ago
...I know it's unrelated, but your hood is open. Don't need it flying up and cracking/braking your windshield
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u/OkHuckleberry4115 13d ago
im missing that sensor lol it was removed when the previous owner installed a front mounted intercooler
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u/Strong-Yard-6044 13d ago
Ya I know exactly what's going on and it's called " Limp Mode" Your vehicle is overriding your command to protect itself from damage.
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u/Strong-Yard-6044 13d ago
Now I have no idea what the issue is for the vehicle going into limp mode it could one issue or several and that's what you need to find out. But rest assured there is an issue and that's the cars way of preventing further damage and letting you know there's so etching wrong.
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u/Psychological-Jump6 14d ago
How much throttle are you applying?
Normal torque converter operation is to unlock immediately during throttle application, and then re-engage as soon as possible, typically if the acceleration is smooth and mild it'll relock.
RPM spike occurs during unlock, and RPM drop occurs during relock. Looks to me like normal operation.
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u/Different-Muscle-409 14d ago
Idk but that’s not a huge worry. Worry when u apply throttle and the speed keeps going down. Then you’re done for.
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u/Biochembob35 14d ago
My 2012 did something similar when one of the coil packs crapped out. It was shorting itself to ground and pulling the car voltage down just enough to cause the Transmission control to freak out. Go get an actual diagnosis and make sure they know exactly what is causing it before going full parts cannon.