Does not accelerate while driving and brakes become stiff

2009 KIA PICANTO
53,000 MILES • 1.1L • MANUAL
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CHRISSG
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  • 2 POSTS
While driving, the car suddenly slows and will not pick up speed much even when you step harder on the gas pedal; usually happen when have to ease on the gas pedal while driving on a gentle up slope. Tried stepping on the brake and realized it was becoming hard. Problem resolved by itself when switched off the engine and rested till the brake stiffness is gone.

No problem light appears on the dashboard at all.

If reversing before rested, the car will jerk and stall.

Replaced the PCV value and check valve to brake booster but problem not resolved.
Jul 6, 2022 at 8:49 AM
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STRAILER
  • CERTIFIED EXPERT
  • 53,872 POSTS
This happens when the brake booster push rod is adjusted out too far. Try this: when the brakes are locked up try to loosen the brake master cylinder mounting nuts two turns to see if the car rolls again. If so, remove the brake master and adjust the rod inwards, if the problem persists, replace the brake master, this guide can show you how.

https://www.2carpros.com/articles/how-to-replace-a-brake-master-cylinder

This video will show you how to bleed the brake master:

https://youtu.be/WDxvEQrMkBg

Check out the diagrams (below). Let us know what happens and please upload pictures or videos of the problem.
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Jul 6, 2022 at 8:23 PM
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CHRISSG
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Hi Ken, I had not done any work on the car except yearly changing of engine oil since 2019. I did change the brake light switch in November last year as the brake light did not work after putting in a new bulb.
Will the brake booster push rod push out by its own? Or should I ask whether changing the brake light switch is causing me this problem six months later and thus I should bleed the brake master?
Jul 7, 2022 at 6:35 AM
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STRAILER
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  • 53,872 POSTS
It could be the booster is starting to wear and not retracting completely. This is normal, anything that holds pressure on the brake master will cause this issue.
Jul 8, 2022 at 3:49 PM