Grand Theft Auto IV Walkthrough

Follow the red dot on your HUD. That dot represents the van, and you have to ram is, damage it, and in any other way hinder it in order to damage it. When the van takes enough damage, it will stop, the driver will relent, and he will offer to pay what he owes. But getting to that point can be tough, and if the van strays too far from your location or if you take too long, you'll fail the mission automatically and will have to try again. Your best bet is to get behind the van and try to shove it in one direction or another. This should cause the van to spin wildly, damaging it as it strikes into cars and other obstacles.

When the driver finally relents after your frantic chase all around the borough, he'll stop, talk to you from his van promising to pay, and then you're off. Since he's promising to pay in the future and didn't actually give you anything, you don't have to go back to visit Vlad, since there's nothing to give him. Instead, the mission will come to a successful conclusion following a victorious, albeit brief, phone conversation with Vlad.