User not able to post iframes in joomla article

I am not able to add iframes to an article as a limited user.

As a super user, I am able to do so because I allowed it in the JCE editor settings. There is an option for user profiles there, so I edited the default one and gave permission to every user. Still when I login as a user with limited rights (no admin rights and no superuser rights) it refuses to save the iframe.

What am I doing wrong?

I am use JCE in Joomla 3.5.1.

You missed this steps set Filter Type to No Filtering in Joomla! Global Configuration, Text Filters tab

Configure Joomla! Article filters

By default Joomla! 'cleans' content on saving, removing script tags, event attributes (such as onclick, onmouseover etc.) and style tags.

A simple article parameter change is all that is required to fix this.

Joomla! 2.5 and Joomla! 3

1. In the Joomla! Global Configuration, click on the Text Filters tab.
2. For the Super Users group, or any other trusted user group, set Filter Type to No Filtering. Make sure that you only set this option for user groups that can be trusted as setting the Filter Type to No Filtering will essentially allow the user to include any html in an article.

Reference https://www.joomlacontenteditor.net/support/faq/item/iframe-removed-on-saving