There's no way to diagnose check engine light with out scanning the code.Have the engine code scanned. Do it at autozone or get a scanner. Cheap ones can be bought for as little as $50 at Autozone, Sears, and Advanced auto parts.If you try to "fix" your problem without the code you are chasing ghosts and you will waste more money than you will save (by not getting a scanner).Good Luck.