Q: My ipad is due an upgrade to ios7.1.1 and it's saying its need 1.9mb space I have over 4.0mb of space it won't let me do it

You need space for the download to expand after it downloads and installs. You will have to delete content in order to update. You have always keep about 10% of your device storage free anyway and the iOS will not let you use every available MB of space that you have on your iPad, so you have to keep that in mid as well.

Start deleting content that you really don't need or want if you want to update. If you have the space after you update, you can download or sync the content back to device later.

Connect iPad to iTunes and Check For Updates (tap to enlarge image)