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RPM acceleration when braking?

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Mr. Detail
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RPM acceleration when braking?

Post by Mr. Detail » Tue Dec 03, 2019 6:56 am

Not sure if this was addressed by me awhile back or not as I checked my profile and any private messages and could not find this topic.
For awhile now whenever I apply the brakes, as in coming to a red light, the engine revs up to 3k or 4k rpm's. It won't come back down until take my foot off the brake pedal.
Any idea what could be wrong or needs replacing? (Ugggh)



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- Pete -
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Re: RPM acceleration when braking?

Post by - Pete - » Tue Dec 03, 2019 7:56 am

Sometimes I accidentally hit the gas when I hit the brakes. If you're positive you aren't hitting both pedals I'd poke my headlamp around under there & inspect the various moving bits to see if anything obvious is hung up.


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Re: RPM acceleration when braking?

Post by jimmy57 » Tue Dec 03, 2019 8:22 am

Brake booster issues can give a sort of vacuum leak but the hose from booster to intake won't flow enough for 3000-4000 RPM. IS the engine actually revving that high or is it electrical and only the tachometer indication going high? Sitting still in neutral rev the engine to that high speed to be sure you know what it sounds like. I would think you have a manual transmission. If it is as auto trans the car would not stop without HUGE pedal effort if engine is running that fast.



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Re: RPM acceleration when braking?

Post by chrism » Tue Dec 03, 2019 9:01 am

Try disconnecting the vacuum hose from the booster and plug the hose. Then see if the problem disappears. If it does then you have a seriously leaking booster.

NOTE: Be VERY careful if you try driving the car with the vacuum hose disconnected as you won't have any power assist and will have to press much harder on the pedal to stop the car.



Mr. Detail
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Mr. Detail

Re: RPM acceleration when braking?

Post by Mr. Detail » Tue Dec 03, 2019 11:29 am

I am definitely not hitting both the accelerator pedal and the brake at the same time.
This wagon has an automatic transmission. Trust me here as I do know what the engine sounds like at 3000 rpm's.
It is the engine revving up and not an electrical issue. I am constantly shifting the car into neutral at red lights so I don't
hit the guy in front of me. Neutral and foot off the brake pedal, then the tach and engine returns to normal 750 rpm's.



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