I absolutely agree with SF, but keep in mind whether you want your translation to be adapted to the target language and culture, or if you want to teach your audience about the original language and culture.
For instance, suppose the original is set in the Wild West, USA... and you're translating it into Chinese. Suppose your target audience wants to learn about American history and culture.
In this case, it would be odd to use the Chinese idiom 毛髮不爽 ("uncombed fur") and introduce a mistake. It would be strange for a cowboy in the Wild West to be so cultured in Chinese proverbs, even if he got it wrong! (It would, however, be acceptable for the narrator to use this expression.)
Instead, I'd translate it as something like this:
He makes me feel... makes me feel...
I'm allowing the reader to fill in the blanks himself. If he doesn't know that Americans don't use the expression "uncombed fur," he's welcome to insert that. But if the reader knows a bit more about American culture, he can insert something else in his mind without finding it strange.
Either way, I have communicated the fact that Jim isn't the most eloquent of speakers.
Translation isn't about conveying the original text itself. It's about transcending language and culture so that you can reveal what's beneath the words.
A good translation isn't bound to the original text. Feel free to use your own creativity to express what the original author wanted his readers to feel.
Of course, this depends on what your audience is expecting. A translation published in the Chinese Journal of American Literature (if such a journal exists) will read very different from subtitles posted on YouTube.
Know your audience, and cater to what they expect.