my 2007 alto vxr giving up and down rpm even stall on patrol while idle. went to mechanic he block a vacuum line which originates from carburetor and end in carburetor. rpm goes stable but after that cars do hiccups both on patrol and cng. unblocking the vacuum line bring car to normal but again on patrol rpm up and down problem. mechanic says some diaphragm is out of order and he block vacuum for patrol line.any one can help me in this regard.