Erratic brake performance due to rough idle?

[WestCoastSVX]

Totally throwing a theory out here.

I have noticed lately that occasionally when I push the brake pedal it will seem to "slip" a little? Very hard to describe. It will start to feel normal, then the pedal will almost feel like it is dropping suddenly to where it is not a smooth push. That's the best I can descibe it.

This is always at very low speed, like navigating a parking lot, and it's never resulted in poor brake performance overall, the car still stops where I want it to stop. But again, we are talking about < 10 mph here. It's never done it at any higher speeds, which is good for safety, and also lends towards my theory.....

Another thing is VERY occasionally, like maybe 1/4 of the time it does the above symptom, it also makes an audible "electronic" type of buzz for a second. Again, hard to describe, but almost like a little pulsing buzzing sound? About 1 second total, and always with that erratic brake behavior (although again, the sound only happens about 1/4 of the time).

I've had the car into a trusted shop to check on some things, this included. They went over the whole braking system and couldn't find anything visually out of place. It's not like they tested the sensors or electronics, but all the physical components looked and acted as they should (and of course on the test drive nothing acted up as usual!). All rotors and pads are brand new, as well as fluid flushed with new. Stainless lines and calipers are at about 20K miles.

So now my theory/question. Could the electronic braking system in the SVX be affected by the rough idle issue I have? At stop lights and low speeds I do have issues with rough/fluctuating engine performance, which I'm working on (probably will do new TPS next). Could this possibly affect the braking system, like is it RPM sensitive, or maybe cause a power drop that affects the electronics? Or am I dreaming and should have a more thorough inspection done on the braking system electronics?

[SoCal LS-L]

Makes sense..... the vacuum may not be sufficient when the idle is stumbling, and when the SVX is going very slow, its always right around idle RPMs. The vacuum in your booster might not be enough to keep adequate boost so that may be what youre feeling. Also the check valve which keeps vacuum applied to the booster even when the car stalls or has momentary low vacuum could be going bad allowing vacuum to leak back into the supply line from the booster.

[WestCoastSVX]

Thanks!

Like I said, my next step is to replace the TPS. I'll report back if this has any effect on this issue as well.

[SoCal LS-L]

Originally Posted by MacGyver

Thanks!

Like I said, my next step is to replace the TPS. I'll report back if this has any effect on this issue as well.

Have you tested it first? Pulling the TPS is pretty easy so its worth the time to test the resistance arc first. Rough idle can be a PITA to diag..... does it do it all the time...or just when cold or warm?

[Hondasucks]

Could be the ABS. My pedal will pulsate slightly if I happen to hit the brakes at the same time that the ABS runs it's self-test. (You can see it at night, when you start that car and hit about 2-3mph while moving forward, the headlights will briefly dim slightly, that is the ABS pump doing a self check.)

[Crazy_pilot]

So THAT's what that is. I had been wondering, I've felt it a couple times when I first touch the brakes in the morning.