Every time i press the clutch the car stumbles ,its like it would shut down like no power

Clutch plate and pressure plate seem to be too weak to pull the car. Or one of the CV joints is detached from the gear box. To test the clutch plate, park the car on flat surface. Pull the hand brake up, start the car, depress the foot brake pedal, depress the clutch pedal, put the car in 1st gear, press the gas pedal and leave the clutch pedal at once, while keeping the brake pedal depressed.
Follow one of the two following statements:
1. Engine does not shut down and remain start. (Clutch plate, pressure plate and clutch bearing defective - Replace all as a set)
2. Engine shuts down. (Clutch system is OK and does not require any repair).

Clutch plate and pressure plate seem to be too weak to pull the car. To test the clutch plate, park the car on flat surface. Pull the hand brake up, start the car, depress the foot brake pedal, depress the clutch pedal, put the car in 1st gear, press the gas pedal and leave the clutch pedal at once, while keeping the brake pedal depressed.
Follow one of the two following statements:
1. Engine does not shut down and remain start. (Clutch plate, pressure plate and clutch bearing defective - Replace all as a set)
2. Engine shuts down. (Clutch system is OK and does not require any repair).

Clutch plate and pressure plate seem to be too weak to pull the car. To test the clutch plate, park the car on flat surface. Pull the hand brake up, start the car, depress the foot brake pedal, depress the clutch pedal, put the car in 1st gear, press the gas pedal and leave the clutch pedal at once, while keeping the brake pedal depressed.
Follow one of the two following statements:
1. Engine does not shut down and remain start. (Clutch plate, pressure plate and clutch bearing defective - Replace all as a set)
2. Engine shuts down. (Clutch system is OK and does not require any repair).

just I would like to ask you a question before giving any answer. Do you have the power shut off at any time you press the clutch ? Is it only just whilst clutch pressed? If so means that either you have worn thrusts on the engine crankshaft,where on applying to clutch you push forward the crankshaft and makes the engine running tighter where it shut off power. My advise is to visit a workshop and request a qualified mechanic to check this case as it is easy for him to get the crankshaft pulley in to his hands,pull and push it and if is what I said he will note the knock .

Stumble off idle,you have a misfire at idle the ignition system is of concern this will include plug wires sparkplugs cap and rotor,

Is the engine light (MIL) on? what are the codes?. I would replace the fuel filter first as it might be bad and if the problem presists then check the fuel pressure.

Sounds like an EGR valve sticking. Start the engine cold and let it warm up. As soon as it starts to hesitate/stumble, pull the vacuum hose off the EGR and if the engine maintains a steady idle, replace the EGR valve. The EGR is sticking intermittently but it won't be long before it sticks all the time and you won't be able to keep the car running when it gets warm. This is an easy diagnosis, removal and replacement for the do it yourself car owners. Please rate me on my answer.

Clutch pressure plate weak.Replace the whole clutch assembely.Hope this was helpfull.

You night be over heating

THERE IS SOMETHING ABOUT THE CLUTCH ON THE SIERRA THAT IF DOUBLE PUSHED DOWN IT ACTS LIKE A CHOKE. CANNOT QUITE REMEMBER. JUST LEAVE IT OUT OF GEAR AND DO NOT PRESS THE CLUTCH. THEY FLOOD. i KNOW THIS SOUNDS STUPID. I HAD ONE ONCE AND AFTER ABOUT SIX MONTHS IT STARTED DOING IT. ITS SOMETHING TO DO WITH THE CLUTCH AND EXCELERATOR AND HOW YOU PRESS THEM. IT MIGHT BE YOU DO NOT TOUCH THE EXCELERATOR AT ALL JUST THE CLUTCH. I CANNOT REMEMBER HAVE A FIDDLE WITH DIFFERENT WAYS OF TRYING TO START THE CAR. CLUTCH DOWN ECCELERATOR DOWN CLUTCH OFF ECCELERATOR OFF. OR EVEN DOUBLE THE CLUTCH TO STOP THE CHOKE. ITS SOMETHING LIKE THAT. PHONE THE DEALER THEY WILL KNOW IN THE WORK SHOP. SAY A SILLY WOMAN SAID IF YOU LIKE. LET ME KNOW.