Why did Nick suggest that Gatsby go away? What was Gatsby's response?

Nick suggested that Gatsby go away because the police would be looking for the owner of the car that hit Myrtle. Gatsby refused because he couldn't leave Daisy, he was still waiting to hear she was leaving Tom.... and coming to him.

“You ought to go away,” I said. “It’s pretty certain they’ll trace your car.”

“Go away now, old sport?”

“Go to Atlantic City for a week, or up to Montreal.”

He wouldn’t consider it. He couldn’t possibly leave Daisy until he knew what she was going to do. He was clutching at some last hope and I couldn’t bear to shake him free.