We present detections of the CO ( J = 1–0 ) emission line in a sample of four massive star-forming galaxies at z \sim 1.5 - 2.2 obtained with the Karl G. Jansky Very Large Array ( VLA ) . Combining these observations with previous CO ( 2–1 ) and CO ( 3–2 ) detections of these galaxies , we study the excitation properties of the molecular gas in our sample sources . We find an average line brightness temperature ratios of R _ { 21 } = 0.70 \pm 0.16 and R _ { 31 } = 0.50 \pm 0.29 , based on measurements for three and two galaxies , respectively . These results provide additional support to previous indications of sub-thermal gas excitation for the CO ( 3–2 ) line with a typically assumed line ratio R _ { 31 } \sim 0.5 . For one of our targets , BzK-21000 , we present spatially resolved CO line maps . At the resolution of 0.18 ^ { \prime \prime } ( 1.5 kpc ) , most of the emission is resolved out except for some clumpy structure . From this , we attempt to identify molecular gas clumps in the data cube , finding 4 possible candidates . We estimate that < 40 \% of the molecular gas is confined to giant clumps ( \sim 1.5 kpc in size ) , and thus most of the gas could be distributed in small fainter clouds or in fairly diffuse extended regions of lower brightness temperatures than our sensitivity limit .