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Old 12-29-2012, 10:19 PM   #3
Scooby Newbie
Member#: 172977
Join Date: Feb 2008
Location: Northern California
2006 WRX TR


Originally Posted by Cobb Tuning View Post
If it happens while pumping the brakes, which requires vacuum power, it would likely indicate an intake tract leak (probably post-TB). It's possible the brake booster supply hose itself is torn.


I checked the brake booster vacuum hose, and everything seemed okay. When I pulled off the hose on the booster side I heard a "swoosh" of air which indicates that it was holding vacuum. I sucked on the hose (I know...very crude and unsanitary) and the hose held a vacuum. The check valve seemed to function properly too. Would I need a stronger vacuum to check the hose?

Do the diaphragms in the brake booster ever leak?

So with your response my misfire sort of makes sense. I'm guessing that my car is still in open loop when I get on the brake at the first stoplight and doesn't accommodate for the extra leaked air from using the brakes, which results in a misfire. Is my logic sound or am I missing something? If this is the case how come only cylinder 1 misfires? Based on my understanding cylinder 4 is connected to the brake booster line and would probably be the cylinder that misfire.

I appreciate the help.

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