I wish I can do it - definately I wish I could do it - possibly, but not definate

I cannot think of any way that 'I wish I can' would ever be used; grammatically it is nonesense. If you 'can' something, then you would not need to wish for it.

Hello Marc "I wish I can" is the present tense. eg : "I wish I can come now" "I wish I could" is the conditional tense. eg : " I wish I could come one day." In this case it is a wish or desire that one day you will come. Both are correct, it depends what you want to say.