I have a 1989 suburban. I have to slam the doors to close them or else they stay partially open. What can I do to solve this. I had an older suburban that did the same thing.

My 86 Suburban and my 86 C10 did the same thing. They had a nylon or plastic bushing on the Torx bolt on the door post that was worn out/missing.
You can buy them in the "Help" section at most auto parts stores but I think you have to buy the kit to get just the bushing. I don't know if your year has these or not? If it does and this is your problem, the Torx bolt threads into a nut plate that is inside the door pillar and if you remove the bolt it will fall and it's a pain to fish it out. Guess how I found out about the nut plate?
Mark around the big washer before you remove it so you will put it back in the same place. I removed the trim on the passenger side between the front and rear doors so I could hold on the nut plate before I replaced the passenger side.

Thanks. I'm off to the auto parts store.