bad master cylinder cause eratic engine idle?

[NISSAN240SX12]

in the past few days my master cylinder has failed. i have to press the brake peddle to the floor to stop the car and its to the point were i cant drive the car. but at the same time my idle is erratic. it revs up and down between 1000 to 1500. the two problems showed up at the same time. Would a bad master cylinder cause this idle issue? I have searched for the past couple of hours and some cars will have this issue if the master cylinder fails. is there anyone that can relate to this and clairify that this is true or false? any input is appreicaited!

[IanS]

Sounds more like a bad brake booster, possibly along with a bad master.

Take the brake booster vacuum line off and plug it, see if the idle flattens out.

[NISSAN240SX12]

Sounds more like a bad brake booster, possibly along with a bad master. Take the brake booster vacuum line off and plug it, see if the idle flattens out.

Thank you. I will try that this morning.

[240ChukiSX]

The idle on my car has been high as well. I replaced the spark plugs and spark plugs wire and they reduced my idle tremendously! I also replaced the master cylinder and it didn't really do much but helped the feel on my clutch. That's all. But the spark plugs, spark plug wires, and fuel injectors is where I would look to fix the idle problem. Lemme kno, and I will try my best to help you.

[Justin35ll]

He doesn't have a high idle, he has a hunting idle. If he has a bad breakbooster with a vacuum leak that will cause a hunting idle.Do what ian said and see if that helps.If not you may need to replace or clean the IACV as well as the brakebooster

[NISSAN240SX12]

The idle on my car has been high as well. I replaced the spark plugs and spark plugs wire and they reduced my idle tremendously! I also replaced the master cylinder and it didn't really do much but helped the feel on my clutch. That's all. But the spark plugs, spark plug wires, and fuel injectors is where I would look to fix the idle problem. Lemme kno, and I will try my best to help you.

Thank you for the tip. I know that i've replaced the wires/plugs and cap about 3 months ago. but worth looking into.

[IanS]

The idle on my car has been high as well. I replaced the spark plugs and spark plugs wire and they reduced my idle tremendously! I also replaced the master cylinder and it didn't really do much but helped the feel on my clutch. That's all. But the spark plugs, spark plug wires, and fuel injectors is where I would look to fix the idle problem. Lemme kno, and I will try my best to help you.

Really? The master cylinder has absolutely nothing to do with the clutch, and bad plugs/wires will not cause a high idle. If anything it will do the opposite.

He doesn't have a high idle, he has a hunting idle. If he has a bad breakbooster with a vacuum leak that will cause a hunting idle.Do what ian said and see if that helps.If not you may need to replace or clean the IACV as well as the brakebooster

Hunting idle, Ive always thought of it more as Honda asthma.

[NISSAN240SX12]

Honda Asthma. LOL thats great!

[sean@z1]

you know a boost leak tester is good for turbo cars and NA cars to find vaccume leaks which is what this sounds like we have them for like 20 bucks

[NISSAN240SX12]

i have a vacuum gauge hooked up to the intake. when i press on the brake pedal the vacuum needle doesn't move. the engine vacumm is 20 HG. but if i pump it up it will dip down by 2 HG and returns back to 20HG

[240ChukiSX]

Thought that he meant the clutch master cylinder. My fault, didn't know that he meant the brake master cylinder. Still kinda new to a few things, but trying to help to the best of my abilities and knowledge. BIG BUMP!