prevents them from firing on all cylinders 
(ROOT (S (VP (VBZ prevents) (NP (PRP them)) (PP (IN from) (S (VP (VBG firing) (PP (RP on) (NP (DT all) (NNS cylinders)))))))))
(ROOT (S (VP (VBZ ) (NP (PRP )) (PP (IN ) (S (VP (VBG ) (PP (RP ) (NP (DT ) (NNS )))))))))