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Discussion Starter #1
I have been having intermittent issues with idle surging. First noticed it when trying to free up a sticky calliper piston and I was pumping the brakes a bunch. It’s getting worse, sometimes it happens stopped at a light with the brakes on.

I think I have it narrowed to the brake booster check valve (the vacuum hose was getting dry too).

Does anyone know if the check valve can replaced on its own or does the entire brake booster have to be replaced? Is it just threaded into the body of the booster?
 

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So what happens?
Idle RPM changes when you push the brake pedal? Sounds normal to me, it’ll change a little bit as it pulls vacuum from the engine
 

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Discussion Starter #3
So what happens?
Idle RPM changes when you push the brake pedal? Sounds normal to me, it’ll change a little bit as it pulls vacuum from the engine
No, no. idle rpm surges 500ish rpms (up and down) if I press the brake pedal rapidly, repeatedly.
 

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Discussion Starter #5
Why would you press it rapidly and repeatedly at idle?
Well like I said, originally I was trying to free up a sticky piston in one of the front callipers.

Now the surging happens if I’m pressing & holding the brake pedal.

the trac control active and the trac control off light come on, on the dash sometimes too.

pretty sure it’s an intake leak or a brake boost/check valve issue....
 

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Discussion Starter #6
After some talks with Alex K, I understand the check valve is in the vacuum hose from the intake to the booster.

So thanks anyway.
 

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Well like I said, originally I was trying to free up a sticky piston in one of the front callipers.

Now the surging happens if I’m pressing & holding the brake pedal.

the trac control active and the trac control off light come on, on the dash sometimes too.

pretty sure it’s an intake leak or a brake boost/check valve issue....
Get the modules scanned, ABS does the trac control
 
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