weird idle during braking.
Thread Starter
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HCF Member
Joined: Oct 2006
Posts: 57
weird idle during braking.
when I hold the brakes on my car the Idle drops and when I release them the Idle goes up to about 1000rpm. When I pump the brakes the idle will go past 1000rpms a little bit and when I release them it drops. I did check the check valve going to the booster and it was fine and just to be sure I replaced it with another one and it didn't make a difference. the hoses look ok so I'm thinking it could be the brake booster or my MAP sensor. I don't want replace the Booster and not have that fix the problem, I don't like throwing parts at the car and hoping it fixes it. I also did notice the pedal travels a little far too. I inspected the brakes and flushed out the system so everything in that department should be okay. BTW my car is a 93ex with the 1.6L vtec.
HCF Member
Joined: Jun 2006
Posts: 3,086
From: West Virginia
RE: weird idle during braking.
I think it might be the booster, spray some carb cleaner on it while the engine is running and see if the idle changes. You can'talways look at a vac line and tell if there is something wrong with it or not.
Thread Starter
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HCF Member
Joined: Oct 2006
Posts: 57
RE: weird idle during braking.
yeah I flushed my brake system(bleed it) I used a vacuum bleeder so I didn't have to pump them, the travel feels kinda far but it just might be how the car is. the brakes stop fine and dont feel spongy. If I can get the brake pedal travel spec I can measure my pedal travel and compare it to see if its off.
Recognized HCF Member
Joined: Sep 2007
Posts: 9,453
From: Houston, Texas
RE: weird idle during braking.
The picture describes how to test the brake booster.
Just a thought: Is it possible that your idle problem might be due to problems with the brake switch, which sends a signal to the ECU to control idle speed? Maybe it would be worth disconnecting the brake switch connector to see if this eliminates the idle problem.
[IMG]local://upfiles/25538/413A88FCD95C4A4296F821A2998BCE61.jpg[/IMG]
Just a thought: Is it possible that your idle problem might be due to problems with the brake switch, which sends a signal to the ECU to control idle speed? Maybe it would be worth disconnecting the brake switch connector to see if this eliminates the idle problem.
[IMG]local://upfiles/25538/413A88FCD95C4A4296F821A2998BCE61.jpg[/IMG]
Thread Starter
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HCF Member
Joined: Oct 2006
Posts: 57
RE: weird idle during braking.
Yeah I forgot to mention that I did hold the brakes and start the car and the pedal did sink to the floor. I have a vacuum gauge IDK if it would help diagnose the problem though.
Chubby Chaser
Joined: Dec 2007
Posts: 4,681
From: whitwell,Tn 37397
RE: weird idle during braking.
i found this in another forum about same problem ...
Try this test for the brake booster, it may help you.
Start engine with the brake pedal depressed. If the pedal sinks
slighty, the booster is working. If pedal height does not change,
booster or check valve is faulty.
Or, Depress the brake pedal w/ engine running, then stop the engine.
Hold pedal down for 30 seconds. If pedal height does not change, the
booster is OK. If the pedal rises, booster is faulty.
Or, With engine off, depress the brake pedal several times. As you push
the pedal the height of the pedal should rise. If it doesn't, the
check valve may be faulty.
Check valve test: Disconnect the vacume hose that runs from engine to
the booster where it connects to booster. Start the engine. If you do
not feel any vacuum, check valve is faulty. The valve is located in
the vacuume hose you disconneted.
I hope this helps.
Start engine with the brake pedal depressed. If the pedal sinks
slighty, the booster is working. If pedal height does not change,
booster or check valve is faulty.
Or, Depress the brake pedal w/ engine running, then stop the engine.
Hold pedal down for 30 seconds. If pedal height does not change, the
booster is OK. If the pedal rises, booster is faulty.
Or, With engine off, depress the brake pedal several times. As you push
the pedal the height of the pedal should rise. If it doesn't, the
check valve may be faulty.
Check valve test: Disconnect the vacume hose that runs from engine to
the booster where it connects to booster. Start the engine. If you do
not feel any vacuum, check valve is faulty. The valve is located in
the vacuume hose you disconneted.
I hope this helps.
Joined: Nov 2007
Posts: 211
From:
RE: weird idle during braking.
Oh yea, it so it begins with the wierd idle. --- Next you get a wierd hissing under the dash like " WTF! " then the brakes become hard as rocks and your like " WTF! " .. so you replace the MC and still no fix... DAMN --- Must be the booster. HEHE Been there, done that!