Can I clear the saved words on my iPhone four?

Its memorised spelling errors and changes the words I want to the wrong ones now.

Can I clear them out while still having autocorrect on?

You can do it in the default keyboard settings

Whenever you spell the word and it comes up with the suggestion just click on the x button after 3 attempts it will learn that it's the wrong spelling and won't offer it as a suggestion anymore.

OR

to delete your entire dictionary and start from scratch
1) Go to Settings
2) Go to General
3) Scroll down to Reset
4) Click on Reset Keyboard Dictionary

* You won't lose any data, contacts, photos, apps, etc this will only clear out your dictionary to factory settings ( so it would be as if you never taught it any words and you'll be able to make sure that it gets the correct spelling of words when you input them*