my nephew has one of this cars and two days ago it stop running, it still turns on but has no power would a plugged catalityc converter cause this problem

yes, a plugged cat converter could cause that. Also could it be the fuel pump or fuel pump regulator? I guess it wouldn't run at all if that was the case.

in all honesty, a plugged cat should not make you lose all power. sounds more like a fuel problem. i would check the inline fuel filter. also, i would check the in tank filter. its on the end of the fuel pump. if they get clogged, the car loses power. if you press the gas and it gets worse, it'll be the in tank filter most definately. have the tank cleaned if that's the problem. what happens is as you press the gas, the pump sucks harder pulling more debris onto the filter, thereby decreasing gas flow to the engine. if its not that, check the fuel lines for clogs. also check to see if any rubber fuel lines are cracked and leaking.

Does the engine check light come on? Did you check for engine error-codes pr. TSRM? Which, by the way can be found here: http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?Section=FI&P=23 I took the liberty to include the direct link to the error code section. A clogged CAT would not cause this amount of loss in power. Also, I doubt it is the fuel-pump, because it would not run if it is defective. The car would run way too lean and the ECU would CUT the fuel completely. Did you put the right gas in there? What happens if you tap the throttle? The throttle cable has a plastic thingy at the end of the rod which can melt. This results in you being unable to actually do anything when you push the throttle. Does Revs go up when you push the throttle?

clogged cat will kill performance. I agree with Tad though. More likely culprit would be the fuel filter

oh yes its would make you lose all power if your have a clogged one the engine will turn over and then cut out my friends beater jeep did that.