You will have to file an extension for yourself. You can't finish your tax return until you get the Schedule K-1 from the LLC. It doesn't matter if you have left the LLC. If you were a partner for part or all of 2016, you have to include in your tax return.
The extension is an extension of time to file your return, but not an extension of time to pay any tax that you owe. If you expect to owe tax with your return, make the best estimate you can of how much you will owe, and pay it with your extension.
