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Discussion Starter · #1 ·
when i press the brakes really hard then let go it makes a very strange shuttering noise, this is done while at a stand still. then if i pump the brakes the idle starts jumping up and down(and no i'm not touching the gas pedal:)). I think its a vacuum problem, but i'm not sure what exactly.
 

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Yeah, because the brakes use the engine vacuum as their power assist. How much does it fluctuate? I think it is normal for a bit of fluctuation, but if you have shuttering, then you could have a problem. Maybe in the brake booster, a vac leak is created when there is pedal pressure? Check out your haynes for checking the brake booster.
 

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Discussion Starter · #3 ·
Ya its fluctuates almost 1200 rpm :s
 

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Discussion Starter · #5 ·
Yes and this is all at a stand still, not while driving, i don't know what else it would be
 

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Just to rule out something to do with the electrical power needed by the brake lights (though you would think that would lower the idle) remove the brake light fuse, and see if the symptoms change.
 

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Discussion Starter · #7 ·
I'll try that tomorrow, thanks
 

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Hmmmm... if engaging the brakes created a vacuum leak, I wonder, would a vacuum leak increase RPM, because more air is allowed into the engine, or lower rpm, because the air hasn't passed through the VAF, and the mixture is now way too lean???

I don't think the current required for the brake lights would trigger the IAC into giving the engine THAT much more rpm to run the alt... but insightful thinking for sure. I know when I flip the headlights on and off, the engine rpm wavers a tiny amount in my car.

If not, check the brake booster for a vac leak, haynes will tell you how to check that.
 
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