pumping brake peddle causes engine rpm to climb 200rpm
Thread Starter
Joined: Jun 2005
Posts: 2,753
Likes: 5
From: Seattle, Washington
pumping brake peddle causes engine rpm to climb 200rpm
Yesterday I had a very stiff brake peddle which required 80 lbs of force to stop the car, today I replaced three rubber hoses that connect the booster to the engine vacuum which fixed the stiff brake peddle but resulted in a new issue.
1) I replaced the rubber hose from the brake booster to the hard line on the firewall
2) I replaced the rubber hose between the firewall hard line and vacuum check valve
3) I replaced the rubber hose between check valve and the location I was getting vacumm.
4) I made sure the check line is pointing the right direction
5) brakes are bled properly
6) all the screw clamps are tight to hoses
I was scared I messed it up when I went to hit the brake peddle. But driving it around the block my brakes were 10X better then before I replaced the rubber hoses. The peddle feel is better too.
Heres where I get confused, when I pump the brake peddle with the car in neutral the engine RPM increases by 100-250rpm.
Whats the deal and what did I miss?
where do I start trouble shooting this?
thanks
oh yeah, I'm using TII booster, brakes and master, probably doesn't matter for diagnosis and troubleshooting since a similar system originally came on the FB
1) I replaced the rubber hose from the brake booster to the hard line on the firewall
2) I replaced the rubber hose between the firewall hard line and vacuum check valve
3) I replaced the rubber hose between check valve and the location I was getting vacumm.
4) I made sure the check line is pointing the right direction
5) brakes are bled properly
6) all the screw clamps are tight to hoses
I was scared I messed it up when I went to hit the brake peddle. But driving it around the block my brakes were 10X better then before I replaced the rubber hoses. The peddle feel is better too.
Heres where I get confused, when I pump the brake peddle with the car in neutral the engine RPM increases by 100-250rpm.
Whats the deal and what did I miss?
where do I start trouble shooting this?
thanks
oh yeah, I'm using TII booster, brakes and master, probably doesn't matter for diagnosis and troubleshooting since a similar system originally came on the FB
Joined: Mar 2001
Posts: 31,837
Likes: 3,234
From: https://www2.mazda.com/en/100th/
when you pump the pedal the brake booster acts like a vacuum leak, so it will change the idle. its normal. every car does it. if you were really bored i think you could play with the idle mixture a little it would help.
and BTW peddle is something you do on a bicycle or a street corner, you push on a pedal.
and BTW peddle is something you do on a bicycle or a street corner, you push on a pedal.
Thread Starter
Joined: Jun 2005
Posts: 2,753
Likes: 5
From: Seattle, Washington
ok thanks man, I'm on a hot streak fixing and adjusting my FB
and yes I am very also bored, I'm going to go play with the idle right now. Tough part is finding a setting that works well when the motor is cold and also hot, I notice if I get the hot idle set where I want then the cold idle turns poopy, if the cold idle is good the hot idle will be higher then I want. I guess somewhere in the middle they should meet
ps thanks for the English lesson too, I find my brain likes to forget most words have 2 variations of spelling. Brake or Break, board or bored, peddle or pedal, meet or meat, LAWL or LOL btw PEDAL is something operated by foot, so a bicycle and a brake pedal are spelled the same.
and yes I am very also bored, I'm going to go play with the idle right now. Tough part is finding a setting that works well when the motor is cold and also hot, I notice if I get the hot idle set where I want then the cold idle turns poopy, if the cold idle is good the hot idle will be higher then I want. I guess somewhere in the middle they should meet
ps thanks for the English lesson too, I find my brain likes to forget most words have 2 variations of spelling. Brake or Break, board or bored, peddle or pedal, meet or meat, LAWL or LOL btw PEDAL is something operated by foot, so a bicycle and a brake pedal are spelled the same.
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Joined: Aug 2011
Posts: 3,078
Likes: 42
From: Cambridge, Minnesota
Well that digressed quickly 
After all the meddling, what does the metal brake booster look like in the metal engine housing - if you don't mind me meddling around?

After all the meddling, what does the metal brake booster look like in the metal engine housing - if you don't mind me meddling around?
it runs along the upper portion of the firewall. it connects to the booster via a check valve and on the other end, connects to the intake manifold via a metal line that has a square block fitting and a banjo bolt
Thread Starter
Joined: Jun 2005
Posts: 2,753
Likes: 5
From: Seattle, Washington
when I was pulling the hose off the square fitting pivoted and took a chip off the lower intake mani, next time I will remove the square fitting all together before trying to pull that dam hose off.
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