What the hell is going on with Solo/Duo Ranked Queues?

I've been in promotions to Platinum IV after a victory streak. Then hell began to me. I won't stop getting matchmade with teammates that suffer of tilt. I've tried every strategy I've been suggested and behaviors to raise up the morale of my matchmade partners. Even roaming just to afford them to be above and take an advantage. But throws are performed, and we get smashed whatever I do. So much effort for nothing. Am I really doing something wrong? At this rate, I'll be losing more LP than what I'm gaining. From Platinum Promotion to Gold II.