When the dreaded Check Engine light comes on, it could be for several causes, potentially expensive, and important to repair.
One culprit is the oxygen sensor. A bad sensor can cause rough idling, poor acceleration, and engine misfires. The longer you drive with one, the worse the damage. It will cost about $300 to replace and you'll probably have to do it every 50,000 miles.
Another cause of rough idling and vibration: bad ignition coils and spark plugs. They may cause stalls and it may be more difficult to start the engine. On the high end, replacing them will be about $500.
Your Check Engine light may also be signaling a bad fuel injector, which could cause misfiring, stalling, and rough idling. You don't want to ignore this repair, which usually tops $400, partly because it can harm the catalytic converter. Break that thing and you'll pay about $1300 to replace it.
On the other hand, the Check Engine light could just be nagging you about a loose fuel tank cap. It will be a sweet $30 to replace it. Always check first to see if the cap is loose or missing when you see the warning light.
Another common cause: the thermostat. Designed to last 10 years or 100,000 miles, a faulty thermostat can cause overheating, noises, and coolant leaks. It will cost about $400 to replace one.
