My "check engine" light is on, and the computer gives a message of "emission leak (small)" or something like that. I took it to a Firestone service station 3 times, and they keep suggesting new things that don't work (a split vacuum hose, replaced gas cap, etc.) Are there any other solutions that are either cheap or likely to fix it? It doesn't affect the operation of the car, as far as I can tell. I just had the coils replaced (all of them) because it was running rough, and thought that fixed it, but apparently not. Suggestions?