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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