Can stimulants affect mobitz type two heart block (wenckebach)?

Mixed Terms: Your question is contradictory. Mobitz i is wenckebach. I suspect you meant 2nd degree heart block. In which case, yes, stimulants increase the overall heart rate, increasing the stress on the lower conduction system we call the his-purkinje system, and increasing the likelihood that it will block. If the problem improves with caffeine, the problem was likely at the av nodal level instead.