Question about 1994 Chevrolet S-10 Blazer

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Very high idle

I have a 94 s10 it has very high idle and it increases when i apply the brake. could it be the brake booster? if it is can i just disconnect the hose and plug it or will my truck brake down?

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  • oumatilla Dec 02, 2008






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Probably is brake booster if you can hear hissing sound, would not advise disconnecting hose, would be extremely hard to stop the vehicle, a dangerous situation. also check for vaccum leaks on intake manifold. follow brake booster hose to engine and check for leak from there

Posted on Nov 30, 2008


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2 Answers

I pulled the brake master cylinder. Since then, it wont idle properly. Is there an adjustment I can do or did I screw something up?

Whatever you did, you screwed up. Check all of the wiring around where you worked and check all the connections for tightness/corrosion..

Nov 22, 2015 | Cars & Trucks

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High idle then stalls as soon as i put my foot on the break iac? would cause that how do i fix it?

It appears that the high idle and stall is occurring because you have a leak in the brake booster unit. When you put your foot on the brake the vacuum side of the diaphragm is subjected to air pressure and it there is a fault, that air is allowed straight into the fuel system which causes a massive lean out and the engine stops. Simple test is to disconnect the brake hose to the manifold and securely blank it off. Start the engine and apply the brakes . If it runs ok then that will be your problem

Jul 28, 2013 | 1994 Saturn Sl

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Truck revs up and backs down when apply pressure to break pedal when idling just had head gasket replaced was not doing this before it was worked on

Sounds like a vacuum leak.
The brake booster uses a lot of vacuum and when applying vrakes the loss of vacuum causes the engine to rev.
Check all your hoses for a disconnect / leak

Feb 24, 2011 | 1994 Toyota Pickup

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1991 chevy lumina euro 3.1 - motor stalls and conks out when comming to a stop and applying the brake - just made it home holding the gas pedal and the brake and keeping the idle high enough not to stall...

It sounds like it could be your brake booster starting to fail. The brake booster is Vacuum operated so it requires suction/vacuum from the engine. When the booster fails it allows the engine to **** all that air and it bypasses the carburator / fuel injection system so then it wants to quit as the wrong fuel and air mixture is getting into the engine.

Quick test - Remove the vacuum line from the brake booster and hold your thumb over the end of the line/ hose. You will feel the suction but when the hose is closed off the engine should run just fine. When the thumb is removed it will idle very rough and maybe even quit. DO NOT drive the car withouth the vacuum hose removed.

Your booster will look something like this When you open the hood and are looking at the firewall on the back of the engine compartment you will see it directly in front of the steering wheel area on the right side. The hose that you want to remove will have an end like this. It could be black or white.

If the booster is your problem, you may want to have a local shop do the install as it is involving your brakes. That is a huge safety factor and you want it done right.

Good Luck.

Feb 18, 2011 | 1991 Chevrolet Lumina

2 Answers

Brakes dont stop suburban till I push real hard

Check brake system. Resurface brake rotors. Replace pads. Check drums and shoes. Fush system. I use cross drilled rotors and carbon fiber pads. Stop in a hurry. Some Suburbans (94 and up) have slow ABS units that take their time to allow brakes to activate.

What age? What Mileage?

Brake hoses go bad and either prevent brakes from operating or prevent them from pulling back after being applied. Had this problem too.

Also check for vaccuum leaks. TBI engines had a loose metal tube under the TBI unit. I had a vaccuum leak and had to tighten my tube 6 times @ 1/4 turn each. Solved problem.

Try to use some liquid around vaccuum hoses and see if idle changes. Non TBI engines have plastic intake issues.

Check check valve in vaccuum booster. My was bad too.

Molded hose neeed to be replaced. I used two hoses and a brake booster filter in the HELP section to make the 90 degree turn from the hard line to the check valve.

93 Suburban 2WD. Runs great now. 16 mpg city.

Dec 15, 2010 | Chevrolet Suburban 2500 Cars & Trucks

2 Answers

How do i change a brake booster


  1. Disconnect the negative battery cable.
  2. Apply the parking brake.
  3. Unplug all necessary electrical connections.
  4. Remove the master cylinder from the booster and pull it off the studs, CAREFULLY! It is not necessary to disconnect the brake lines.
  5. Disconnect the vacuum hose from the check valve.
  6. If necessary, remove the brake light switch.
  7. Disconnect the booster pushrod at the brake pedal.
  8. Remove the booster mounting nuts, located on the inside of the firewall.


Fig. Fig. 1: Vacuum booster mounting

  1. Lift off the booster and remove the gasket.

To install:
  1. Install the booster with a new gasket.
  2. Tighten the booster mounting nuts to 21 ft. lbs. (29 Nm) on all except 1996-98 models. On 1996-98 models, tighten the nuts to 26 ft. lbs. (36 Nm).
  3. Install all remaining components.

Oct 29, 2010 | 1998 Chevrolet Blazer

2 Answers

Engine increases rpm when brake pedal is depressed

Inspect brake booster vacuum line from engine intake to brake booster for leaks also inspect brake booster check valve, more than likely your brake booster is causing a vacuum leak to your Intake thus leaning mixture wich increases idle rpm

Apr 03, 2010 | 1990 Toyota Pickup

1 Answer

Surge in idle when brakes applied or after driving..

block off vacuum hose to brake booster and see if idle returns to normal if it does you need new brake booster has hole in diaphram internally some times slight hissing noise is evident in cab when pressing brake pedal to section where engine surges or idles high. also check for fuel leaks from hoses if you can smell fuel in engine bay while running and engine warm some leaks only leak while running and hot

Jun 14, 2009 | 1992 Nissan 300ZX

1 Answer

Stalls while driving

check the vacumm hose to the brake booster. it might have a leak causing a slight increase in idle and a kill prob when brakes ar applied. good luck

Sep 20, 2008 | 2001 Jeep Grand Cherokee

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