The universal "hidden warranty"
Every car sold in the United States comes with a warranty you may not be aware of. It covers a variety of components for up to ten years or 100,000 miles. This is a set of "emissions warranties," designed to ensure that cars do not pollute as badly as they otherwise would. It places the burden of emission system reliability on the automaker, so they have to find ways to make the car stay "clean" for as long as they can, or pay to fix it.
Check your warranty booklet for details. 1993 models, for example, covered not just the obvious emissions-related items, but also the coil, fuel injection, spark plugs, speed and temperature sensors, throttle body, turbocharger, even secondary ignition wires. (Some of these items are only covered to the first replacement interval - e.g. spark plugs may be covered until 30,000 miles or so).
If your dealer gives you trouble - some claim ignorance and refuse to believe the booklet that comes with the car! - try calling the company at the phone number in your owner's manual. If that fails, or for more information than you get with your car, write to:
Director, Field Operation and Support Division (6406J)
401 M Street Southwest
Washington, DC 20460
If you think it is wonderful that you may be able to get your car fixed because of these warranties, consider in the next election whether you are voting for someone who considers laws like this to be "throttling industry" or "customer protection."
There are some restrictions on this. First, I believe that to qualify for the warranty, you have to fail inspection. Therefore, if your state supplies them, go to a state inspection service rather than your dealer to get the car inspected! Second, you have to be operating the vehicle within the US (maybe or Canada) and within normal parameters. For more, check the book in your glove compartment!
Other laws for your protection
Some states, notably California, have additional laws for your protection. Get to know them. They are in your glove compartment! (Well, they were when the car was new). Details on lemn laws are also provided in your glove compartment (for most states).
Hidden warranties that we know about
Most auto companies will voluntarily fix common problems that are basically due to manufacturing or design defects. For example, Chrysler covers their four-speed automatic transmissions from some years through 10 years or 100,000 miles. A neighbor received a new body computer on his long-out-of-warranty minivan for free. Call the company - it can't hurt to try. (Note that the "silent warranty" is a widespread practice of dubious legality, and car companies are unlikely to admit they exist, especially if you call them secret or silent warranties).