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Brake pedal lowers RPMs

01-22-2014, 12:52 PM
1999 Saturn SW2. Here's a video of what's happening:


When the car is in park, pressing the brake pedal can make the RPMs go down, although sometimes it does nothing. Also, sometimes pressing the brake pedal kills the motor, especially if I put it in Drive or, even more so, if I put it in Reverse. Furthermore, my turning and hazard lights are now cutting in and out: sometimes they work, sometimes they don't.

As far as I can imagine, here are some options of what might be faulty:

fuel pressure regulator
coolant temperature sensor

01-22-2014, 05:03 PM
Sounds to me like a vacuum leak in the brake booster causing the rpm and stalling problem. As far as the light issue, could be a hazard switch or a turn signal switch issue.

was not able to watch the video.

01-22-2014, 06:57 PM
I tried replacing the brake booster check valve: that wasn't it.

I also tried pulling the brake booster hose off: that didn't make the symptoms go away. When in park, touching the brake pedal killed the motor.

Another clue: I just replaced the spark plugs. They were a mess -- crud all over and smelled like gas.

Could it be the fuel pressure regulator? There's a vacuum hose going to it.

01-23-2014, 10:54 AM
With an automatic transmission car running in park with the brake booster cable off, should stepping on the brake kill the motor? If so, then maybe it is a vacuum leak with the brake booster or brake booster hose.

01-24-2014, 03:07 PM

1. My brake lights don't come on.

2. When I remove the brake fuse, pressing the brake pedal doesn't affect the motor.

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