When the car is idling and I press the brake, the engine reve move up and down about 300 revs. Is this normal or a problem. the car idles rough.

 

Sounds like a vacuum leak.

 

the idle will move a little bit because the brake is vacuum assisted, but 300rpm is a bit much.

check the large vacuum hose (about 1/2") running form the manifold to the brake booster for leaks.
when someone presses on the brake, listen for air noises aorund the brake booster as well to see if the diaphragm is leaking.
could also be the check valve on the booster line.

those are the most common places to see issues here.

last thing..
when you press the brake down, which way does the RPM move? up or down?
does it stabilize while you have your foot on the brake, or does it only go back to normal idle when you let off the brakes?

 

Idle moves down when the brake is pressed

it stabilizes at the lower RPM if the brake is kept depressed and goes back when released

 

sounds like a vacuum leak inside the booster.. when you have someone push the brake, stick your head near the booster and listen for hissing.

 

If thats what it turns out to be, whats the solution ? replace the booster ? JY part or new? Or is it fixable.

 

it is fixable, but not by the average mechanic. mostly due to lack of parts.
a rebuilt booster should be in the $100 range.

 

what he said.

 

lol looks like Matt is always gets beat to posting the solution..recently at least, I've seen quite a few of these already. isnt it a great feeling when you can just say that?

 

actually I nailed the problem my first post. the rest of the thread was spent helping him diagnose the issue. Brian was about 4 hours behind.

 

Doesnt that feel great too

 

some of us have lives

I unfortunately was at the hospital visiting a friend in the BICU

 

Fixed.The screw down clip on the hose from the plenum to the booster was loose. Amazing how much trouble that caused , even though the hose itself was properly.

 

*cough* postwhore! *cough*

 

Heh... that was easy. at least it was cheaper than a brake booster! (And I still nailed it in my first post. )

 

You really think so? I've never considered myself that bad of a *****.