Check Engine

Okay guys, I know this should be in the Eclipse forum since it's pertainign to an Eclipse but I already posted there and they didn't help too much. So I'm hoping this is some kind of a universal problem that could be diagnosed here....

My sister has a '97 Eclipse GS automatic and her check engine sign came on and I have no idea what it is. The first time it came on we replaced the spark plugs and the light went away. About a month or so later, the light came on again and this time, we changed the chord (or coils or whatever they're called) that was connected to the spark plugs and the light went away again. About a month later again, the light's back again. 2 weeks ago I checked to make sure all the coils were in all the way and pushed everything in and the light went away again. Bu today, it's back and even after my "checking and pushing," it's still there. Does anyone know what it could be? Ugh, this is frustrating! The guys over at the Eclipse forum said to take it in to AutoZone and rent their computer tester to run the test but the one's around here either don't have the tester, or they say that they don't cover the '97 Eclipse. So yeah, if anyone has any idea what it could be please let me know because I don't want to spend $50 to just run a test. :( Thanks guys.

First off, Autozone should do it for free.
2ndly, if you do have to rent it, they should have a policy where you put in a deposit, and then get the deposit back when you bring the tool back...Autozone is a chain, I don't get why yours would be different from the ones I go to.
And the reason the people in the Eclipse forum said get the ECU codes run, is because that is the #1 thing to do...it diagnoses exactly what the problem is.

Even if it does cost $50, that is still better than spending a few hundred on parts that don't need replacing.

Yeah, if we rented it, we'd get the deposit back but there's no point in renting the thing when they say that they don't have the car in their system. Don't know why that is but that's what they said.... Anyways, so no idea on what to check?

97 should be OBDII, so I don't see why they wouldn't have it in their system.
Repost in the Eclipse forum and ask if they know how to pull the codes manually. I know plenty of people that have done it on Honda Accords...

The CEL will come on for many different reasons. You need to pull the CEL code, and find out what that code means. That will tell you what needs to be replaced. The CEL isnt as simple as the other warning lights that come on.