How do you change the pcv valve on a 1993 Toyota Paseo?

First, locate the pcv valve. It is on the top of the valve cover in the center of it and has a small hose(about 4" long) going into the intake manifold. Now you will need needle nose pliers to remove the clamp from the pcv valve. Take your pliers and grab the round clamp at the two ends facing up and squeeze until the clamp opens. While holding the clamp open, gently move the pliers left and right while pushing towards the intake manifold. Once the clamp has moved off the valve, release the pliers. You should now be able to remove the rubber hose from the valve. Pull the hose off the valve. Now that the hose is removed, you should see the plastic end of the valve(right angle shape) Next, hold the valve at the base of the grommet(this is on the valve cover) pull up on it while twisting it back an forth. This part may be a little hard as some pcv grommets are tighter than others. Removed it little by little. Don't try to pull it out all in one shot or it might snap apart. I'd recommend getting your replacement pcv valve from the dealer. I've seen some aftermarket valves not work properly. Now the reinstall. Take your replacement and put a small amount of oil(very little) on the valve where it inserts into the valve cover. push straight down on the top of the valve until it is fully seated. When the valve is fully seated, you should be able to turn the top of the valve into position facing the intake manifold. Now, attach the hose to the new pcv valve and use pliers to move the clamp back into place on the hose. You will notice a ring shaped imprint in the hose where the clamp should be seated. Good Luck!!!

edit: I advise also replacing the grommet since it will eventually get so hard and brittle that when you do have to replace it it will break up and pieces will fall into the engine.