The striker, a free agent who joined the West Country side from Spanish outft Cadiz, had only been on the field for seven minutes when he rose to head home a left-wing cross.
The late strike ended Plymouth's 50-year wait for a league win at Coventry.
City could have taken the lead in the second minute when they strung together a good early move. Kevin Kyle won the first of many headers and, when Jay Tabb played the ball in to Stephen Hughes, the home skipper forced a save out of Luke McCormick.
It was a deceptively lively start and the action didn't pick up again until the 13th minute when Tony Capaldi came close to netting - at the wrong end. The left-back had little choice other than to react when the ball was flicked on inside the Plymouth area and had to watch as his attempted clearance dipped just over the bar with McCormick stranded.
The visitors spurned a chance to open the scoring in the 14th minute when Reuben Reid wasted a superb opening with some very poor finishing.
David Norris ran 60 metres when a Coventry corner move broke down but, having put Reid in, the striker struck the side-netting.
But the chance seemed to spur the visitors into action and, with the impressive Akos Buzsaky running midfield, they looked dangerous.
Norris went on another charge in the 21st minute and unsurprisingly chose not to pass to Reid but went for goal only for Elliott Ward to block the effort well.
Andy Marshall was then called into action when Marcel Seip beat the Coventry defence with an excellent pass which took out Robert Page and fell to Nick Chadwick who forced the keeper into a fine save.
The visitors were on top and Buzsaky's whipped cross just eluded the outstretched boot of Chadwick at the back post.
Plymouth started the second period on top and both Buzsaky and Lilian Nalis went close for the away team as Plymouth continued to press in a bid to break the deadlock.
Coventry's chances were few and far between but Stern John should have done better in the 54th minute when he turned in the box but hit a tame effort into the hands of McCormick.
Micky Adams sent on Don Hutchison and Dele Adebola to try to pep up his attack but it was Plymouth who looked most likely.
Reid spurned another opportunity to score on his debut when he was set free in the 71st minute but shot wide from a tight angle.
Then, with nine minutes left, Plymouth got their just rewards for all of their pressure.
Hasney Aljofree planted a perfect cross onto the head of Samba who rose above everyone and powered his header past Andy Marshall.