1994 Toyota Tercel idle

Here's a brief video on idle adjustment:
http://www.youtube.com/watch?v=aXzDZSNSHJE
If the slow idle is a recent change ... then of course you
need to find the problem.

vacum leak find fix

Can't hurt...a local Autozone can do it too.

Clogged or Damaged FreshAir Intake Hose.

Could be your idle air control valve.

Please check your groundings, you can use the 5points grounding system.

Check for split hose's around the inlet manifold.Sounds like a vacuum leak.
Hope this helps.

A clogged fuel injector would make the engine shake, and your power would be compromised.
Whe you changed the plugs, did you put Toyota plugs in, or a different brand? More often than not, using any other plug than plugs bought at a Toy dealer can make the engine run worse. The engines are designed with a specific plug. Also, replace the wires if they are older than 5 years.

Although this isn"t a proper fix, and may affect emissions, I ran accross this problem on a friend's 87 2wd wagon.

There is a dashpot that controls a lever the Idle set screw is on, I am guessing it is a decel valve that closes butterfly when coasting in gear. I never looked at a manual to figure out what controls the vacuum valve that is on the passenger side of the engine compartment, but if you disconect the vacuum line and plug it that lever will not back off and idle will remain where you set it with the adjustment screw.

Make sure the engine is warmed up and not on a fast idle cam before adjusting idle.

The car is a 5 speed, I not sure if automatic cars are the same.

The car idles fine now and still run's great and gets 37+ MPG with 240000 miles!

If you want to fix it properly you would have to diagnose why that dashpot is being actuated at idle