afnan, your txv is sticking or there is a restriction within the evaporator coil if your condenser is new, for flushing I first use a standard solvent like petrol or white spirits and then finish off with acetone (lots of it). While using the petroleum solvents its best to fill up and use air pressure to make a hammer effect inside.
Please note only pipes can be cleaned this way not the coils - multipass coils are best renewed as the orifices are tiny. Also note that if your suction line has a manifold on it then renew that line, the manifold piece cannot be cleaned out.
now back to your issue, you mention that someone has patched the liquid line to repair something, I hope that the line has not been compromised internally - you will feel it mostly as a drop in temperature after the restriction.
