Cherokee 4.0

I have no power brakes, they been slowly going out and have been out for a month or so, plenty of braking power and now i got a strong right leg from getting used to it. It hisses when i press on it and if im sitting at a light with my leg on the brake, and take it off it goes for 750 rpms to well stalling out? I was told by the guys at auto zone my booster SEEMS to be ok...and i just read in the website:
Dear Tom: I own an '87 Jeep Cherokee. (See 2008 Jeep Grand Cherokee)During the spring and summer when I start the car, it begins idling at almost 3500rpm. It doesn't happen during the colder seasons though.
It idles very high and quite loud until it warms up. While it is warming up, I can smell something burning. I get nervous and have to turn the car off. Also, if I drive it while it is idling at this high rate, the brakes are extremely hard to push.
I've taken it to many mechanics (even the Jeep dealership) and the response is either: (1) Probably the idle is stuck, so just tap the gas pedal; or (2) The problem didn't happen for them so they have no advice. Please help me locate the problem so I can tell them exactly what is wrong with my car.
Marcus from Richmond, Virginia
TOM: What you're describing sounds like a faulty power brake vacuum booster. Either the diaphragm in the brake booster is torn or the vacuum circuit going to the booster is cracked or broken.
With an excessively high idle and no power brake assist, you are an accident waiting to happen. This needs attention right away! Also, there have been lots of problems with the nylon vacuum hoses that control crankcase ventilation on this model. When these molded lines crack, the engine cannot properly ventilate. This can cause oil leaks and the air cleaner housing to fill with engine oil, which could be the source of the burnt oil smell. Get it fixed ASAP!
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so also my exhaust have progressively become more smokey and everything, so whats my problem and are the smoke and brakes connected

Abovetimberline

it is possible your diaphram is cracked or leaking,that would exsplain the hissing sound,the reason it would die is you are actually causing a huge vacuum leak when you press on the pedal.

Cherokee 4.0

so i need a new boaster?

Abovetimberline

It is possible,A hard pedal is an indication that your booster is bad along with the other problems you mentioned. Before you replace it I would take the time to read about boosters on the internet,they are very simple.

ol"blue

Usually a vacuum leak causes a fast idle. As a test, disconnect the vacuum line that goes to the brake booster and plug the line. If your engine problems go away there's your answer. JMO
Dan

BuckB91XJ

Hard brake pedal, hissing when you press the brake pedal, idle issues...um....bad Power Brake Booster. Save yourself a lot of wasted time and just swap it out.Sometimes when certain parts go bad it's just a no-brainer what the problem is.

Cherokee 4.0

yeah i was 100 percent thinking it was a booster to the guy at auto zone said the booster seemed to be there......

G_P

the booster may still be physically there but that does not mean it is still working properly. It sounds like you have a wicked vac leak in there.

Cherokee 4.0

im saying it was working i guess the pedal dropped when he turned it on