Isuzu Trooper Shifts hard and Engine Revving in stop?

Inspect the throttle body and idle air control valve closely.It also sounds like carbon is sticking the throttle control open on this car.
While the engine is revving high remove the throttle cable at the throttle shaft. If the RPM does not return to an idle, remove the air intake hose [in front of the throttle plate] Check that the butterfly is all the way closed. If so then replace the TPS.
In some cases cable gets stuck up.
In throttle body area there are two lines one for the actually gas pedal and the other for the cruise control. What happens is the cable gets stuck, causing the engine to rev high, normally if you just drive around the cable goes back down.If all this checked ok and there is power brake system on your car then its Vacuum leak.
Vacuum leak sounds right. It might be inside the booster. Try plugging the line to the booster to see if it idles better. Or listen carefully under the dash for a hiss when you push on the brake.
The booster is on the firewall in front of the driver. In other words, it is to the back right of the engine compartment as you look under the hood.If all checked ok,then it can be Faulty brake booster causing the fault.

See how the brake booster looks.

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This details will help you.

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If you need dis-assembly or replacement instructions for any other auto/car part, or you want to ask question related to your car/truck jeep problem then please leave the comment with your details, so I can provide you the required instructions and solutions.

For more brake related help solutions,see the list below :----

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How Anti-Lock Brakes Work?

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Car Brake lines have no pressure?

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Where is Power Brake Booster located on 1995 Lincoln Town Car?

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How to Replace Power Brake Booster on 1996 GMC Jimmy?

http://schematicsdiagram.blogspot.com/2011/12/how-to-replace-power-brake-booster-on.html

Abs and service light comes on?

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ABS light stays on but brakes work fine?

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VCS maintenance required on Toyota Camry?

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VCS and ABS lights go on and off intermittently on Lexus?

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ABS & Brake lights warning indicator steady on dash and speedometer not working for Dodge Ram?

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E-brake is stuck down on Ford Focus?

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When the car stops, abs pump turns ON?

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Sometimes ABS light comes on while Driving?

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How to Disconnect Power to EBCM on Pontiac Grand Prix?

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Where is ABS/TCS module located on 2005 Cadillac Deville

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How to Replace Power Brake Booster on 1996 GMC Jimmy?

Most all modern vehicles use power assisted brakes. A vacuum line from the intake manifold to the brake booster provides a source of vacuum.Most power brake boosters are vacuum operated devices requiring approximately a minimum of 17 inches of vacuum to operate. The brake booster is the round, black canister located at the back of the engine compartment on the driver's side of the Vehicle.It uses vacuum from the engine to increase the force that your foot applies to themaster cylinder.

The power brake booster is a tandem vacuum suspended unit. Some models may be equipped with a single or dual function vacuum switch which activates a brake warning light should low booster vacuum be present. Under normal operation, vacuum is present on both sides of the diaphragms. When the brakes are applied, atmospheric air is admitted to one side of the diaphragms to provide power assistance.

Follow the procedure mentioned below for REMOVAL & INSTALLATION of power brake booster on your GMC Jimmy.

1994-97 Models

See Figures 1 and 2
Apply the parking brake and block the drive wheels.
Remove the master cylinder-to-power brake booster nuts, then reposition the master cylinder and combination valve out of the way; if necessary, support the master cylinder on a wire to prevent damaging the brake lines.
When removing the master cylinder from the power brake booster, it is not necessary to disconnect the hydraulic lines, therefore the brake system should not have to be bled.
Disconnect the vacuum hose from the power brake booster.

See the diagram below:----

 


Fig. Fig 1: Common power brake booster attachment

From under the dash, remove the retainer and washer from the brake pedal on 1994 utility models. On all other models, remove the retainer and brake switch from the brake pedal.
Disconnect the pushrod from the brake pedal.
From under the dash, remove the power brake booster-to-cowl retaining nuts.
Back under the hood, remove the power brake booster and the gasket from the cowl.
To install:

Position the booster to the cowl using a new gasket.
Install the bo oster retaining nuts and tighten to 16 ft. lbs. (22 Nm) 1994 utility models, 24 ft. lbs. (32 Nm) on 1994 pick-up models and 27 ft. lbs. (36 Nm) on all 1995-97 models.
Connect the pedal pushrod and install the washer or switch and the retainer.Connect the vacuum hose.

Fig. 2: Checking the piston booster rod using the gauge tool
For all vehicles cover ed in this guide, gauge the booster rod:
Apply 25 in. Hg (85 kPa) of vacuum using a hand held vacuum pump or apply maximum engine vacuum.
Chec k the maximum and minimum rod lengths using J-37839 or an equivalent pushrod height gauge.
If the piston is not within limits, install a service adjustable piston rod and adjust it to the correct length.
Reposition the master cylinder and combination valve bracket to the booster studs, then secure using the retaining nuts. For details, please refer to the master cylinder procedure located earlier in this section.
Start and run the engine, then check for proper booster operation.

This details will help you.

----------

If you need dis-assembly or replacement instructions for any other auto/car part, or you want to ask question related to your car/truck jeep problem then please leave the comment with your details, so I can provide you the required instructions and solutions.

For more brake related help solutions,see the list below :----

Brake System Troubleshooting?

http://technoanswers.blogspot.com/2011/11/brake-system-troubleshooting.html

How Anti-Lock Brakes Work?

http://technoanswers.blogspot.com/2011/11/how-anti-lock-brakes-work.html

Car Brake lines have no pressure?

http://schematicsdiagram.blogspot.com/2011/12/car-brake-lines-have-no-pressure.html

Where is Power Brake Booster located on 1995 Lincoln Town Car?

http://howtobyme.blogspot.com/2011/12/where-is-power-brake-booster-located-on.html

Abs and service light comes on?

All types of brake problems and repairs

http://howtobyme.blogspot.com/2011/11/abs-and-service-light-comes-on.html

ABS light stays on but brakes work fine?

http://howtobyme.blogspot.com/2011/11/abs-light-stays-on-but-brakes-work-fine.html

VCS maintenance required on Toyota Camry?

http://howtobyme.blogspot.com/2011/11/vcs-maintaince-required-on-toyota-camry.html

VCS and ABS lights go on and off intermittently on Lexus?

http://howtobyme.blogspot.com/2011/11/vcs-and-abs-lights-go-on-and-off.html

ABS & Brake lights warning indicator steady on dash and speedometer not working for Dodge Ram?

http://howtobyme.blogspot.com/2011/11/abs-brake-lights-warning-indicator.html

E-brake is stuck down on Ford Focus?

http://schematicsdiagram.blogspot.com/2011/12/e-brake-is-stuck-down-on-ford-focus.html

When the car stops, abs pump turns ON?

http://howtobyme.blogspot.com/2011/12/when-car-stopsabs-pump-turns-on.html

Sometimes ABS light comes on while Driving?

http://howtobyme.blogspot.com/2011/12/sometimes-abs-light-comes-on-while.html

How to Disconnect Power to EBCM on Pontiac Grand Prix?

http://schematicsdiagram.blogspot.com/2011/12/how-to-disconnect-power-to-ebcm-on.html

Where is ABS/TCS module located on 2005 Cadillac Deville

http://schematicsdiagram.blogspot.com/2011/12/where-is-abstcs-module-located-on-2005.html

How to Bleed Brakes?

Park your vehicle on a solid level surface and set the parking brake.Open the hood and locate the brake master cylinder reservoir.

Photo may not be specific to your vehicle

Siphon the old brake fluid from the master cylinder reservoir with a turkey baster. Refill the reservoir with clean brake fluid that meets OE specifications (DOT 3 or DOT 4).Using a floor jack, lift up the front of your vehicle and support it with jack stands. Then lift up the rear of your vehicle and support it with jack stands.

Photo may not be specific to your vehicle

Place a 1 x 4 block of wood under the brake pedal to prevent the pedal from traveling too far.Locate the brake bleeder valve behind the right rear wheel. The bleeder valve is attached to the brake wheel cylinder or the brake caliper.Install a piece of clear plastic tubing over the brake bleeder valve and insert the other end into a clear container, filled with 2 to 3 inches of clean brake fluid.

Photo may not be specific to your vehicle

Have your assistant pump the brake pedal several times and then hold it down.Slowly open the bleeder valve. After the old fluid and air bubbles stop flowing, tighten the bleeder valve and then have your assistant slowly release the pedal.

Photo may not be specific to your vehicle

Repeat this process until clean fluid comes out of the bleeder valve and there are no more air bubbles.

Check and refill the master cylinder. Do not allow the master cylinder to drain completely.Repeat the bleeding process for the rest of the wheels in the following order: Left rear wheel, right front wheel, left front wheel.Verify that the master cylinder reservoir is full and you have a solid brake pedal. Lower the vehicle to the ground and perform a road test.

How to Replace a Brake Booster?

With the engine off, step on the brake pedal several times to relieve the brake booster of vacuum.Press the brake pedal down and start the engine. Verify that the brake pedal sinks slightly. Turn off engine.Remove the vacuum hose from the brake booster.Remove the brake lines from the master cylinder. Remove the master cylinder from the brake booster. Plug the fittings to prevent brake fluid seepage.Disconnect the brake pedal from the push rod.Have an assistant hold the brake booster from inside the engine compartment. Remove the nuts that hold the brake booster to the firewall. These nuts are usually located under the dash on the interior of the firewall.Remove the brake booster.Install the new brake booster to the firewall. Tighten the mounting nuts.Connect the push rod to the brake pedal.Connect the vacuum hose to the brake booster.Attach the master cylinder to the new brake booster and reconnect the brake lines.Bleed the brakes at the master cylinder.