Originally Posted by Racer_X

By rough idle, do you mean that it idles OK, then coughs or stumble from time to time? And the engine shakes when it sputters? Does it clear if you just barely press the gas pedal? Those symptoms are usually a dirty idle air control valve and clogged idle air passages in the throttle body.

Get a couple cans of "throttle body/intake" cleaner. Pull the idle air control valve. It's behind the throttle position sensor on the driver's side of the throttle body. There's a narrow air passage from the top of the throttle body behind the throttle bore down into that area. You'll probably find a bunch of carbon on the IAC valve plunger, and enough black "charcoal" in the air passages to have a barbecue. It's a little easier to thoroughly clean all the passages if you pull the throttle body off the plenum. Clean the bore for the IAC vlave, the passage above and the passage below until you see all shiny, clean aluminum, and clean the IAC valve plunger until it's nice and smooth. Put everything back together and see how much that improves things.

If vibration and noise are more noticeable when in drive than in park or neutral, your motor mounts might be week/broken as well.

Originally Posted by thethrill

Finally got it fixed.

Radiator was bad. Replaced and now runs perfect temp.

Distributor was bad, replaced and idles perfect.

Originally Posted by Tuna

You probably covered this, but I learned the hard way recently driving out of Florida, that you can suffer greatly from the lack of a $5 radiator cap. I will always carry a new one in the vehicle as a spare from now on.

You have my sympathies, as I too have found that the Blazer is the most problematic vehicle I have ever owned, and I'm sure I have more than a few years on you.