brake pump at idle rmp drop?

[subaruferrucci]

So i was noticing today that if my car is at idle and i pump the brakes a few times (3 or more times) that the car almost stalls then the RMP goes back up to 1k rmp for a min then settles back down to normal idle levels.

anyone have this happen to them?


I have a light weight pulley and full header back exhaust

[bryan]

Originally Posted by subaruferrucci

So i was noticing today that if my car is at idle and i pump the brakes a few times (3 or more times) that the car almost stalls then the RMP goes back up to 1k rmp for a min then settles back down to normal idle levels.

anyone have this happen to them?


I have a light weight pulley and full header back exhaust

I just tried this earlier today and my car exhibits the same symptom!

I pulled into the garage and while at idle, I pumped the brakes several times. The engine RPMs dropped below 500 and then returned back to idle. I couldn't get the engine to completely stall though, no matter how many times I pumped the brakes.

It's disconcerting but hopefully won't be an issue or anything more serious.

[subaruferrucci]

I am curious if they put to big of brake booster in the car. Uses to much vacuum and robs air from the intake.

I have a friend that says when he is racing it feels like he is running out of vacuum pressure during his autox runs

[Mac1235]

RPM RPM RPM RPM You called it RMP several times, it hurt.

[Draco-REX]

Normal. Every car I've ever owned with a vacuum brake booster will see an idle dip if the brake is pumped quickly. You're just messing with the vacuum in the intake when you do that which distorts the MAP readings. Don't worry about it. There's no need to rapidly pump the brake pedal at idle.

[Freeman]

Originally Posted by Draco-REX

Normal. Every car I've ever owned with a vacuum brake booster will see an idle dip if the brake is pumped quickly. You're just messing with the vacuum in the intake when you do that which distorts the MAP readings. Don't worry about it. There's no need to rapidly pump the brake pedal at idle.

so this would explain the phenomenon of idle dropping to 500 when i come to a quick stop then? maybe?

[Rayme]

Stop doing it and it won't happen.

[Draco-REX]

Originally Posted by Freeman

so this would explain the phenomenon of idle dropping to 500 when i come to a quick stop then? maybe?

That is a separate issue. The ECU expects the MAP readings it gets when the throttle closes. Pumping a vacuum-boosted diaphram behind the throttle plate is not expected. If your idle drops when coming to a stop, that's been documented as an ECU/AVCS issue.


Saw this post and had to do this:

This man walks into the doctor's office and says, "Doc, my arm hurts when I do this!"

So the doctor replies,

Originally Posted by ottopilot

Stop doing it and it won't happen.

[subaruferrucci]

never had a car almost stall its self out after pumping the brake at idle. sound labored but not almost stall like that. and it also happens when i am just coasting to a stop while slowing with the brake then go to a full stop and the RPM dorp