Get Driving To Get Ready For Emissions Inspection

Dear Car Talk:

I recently took my 2015 Honda Civic in for an emissions inspection so that I could renew my registration. The car has 34,000 miles on it. The mechanic says "You have not driven the car much. Go drive it more and come back for re-test."

What kind of nonsense is this? During the pandemic, my wife drove that car probably a mile or two a week, and she continues to log no more than two miles per week. Is there a law that people like us, who don't drive much, cannot register a car? -- Srikant

No, there's no law against not driving much, Srikant. In fact, they should give out medals for it.

Here's what's going on. Emissions and smog tests these days are performed by the car's own computer. Your car's computer is constantly analyzing your exhaust. Kind of like my wife analyzes my exhaust -- then flees the room.

Anyway, the computer analyzes the stuff in your tailpipe to see how well your engine is burning its fuel. With that information, it constantly makes adjustments to the fuel and air inputs to keep pollution low.

Since your computer is collecting all of this information anyway, when you go in for an emissions test, the mechanic simply plugs his scan tool into a port on your car and asks for the data. The computer then reports how much carbon monoxide, carbon dioxide, unburned fuel and nitrous oxides your engine is producing. But before it will even issue the report, the computer performs a "readiness test." The readiness test is all about your fuel system pressure.

Unless the computer can verify that your fuel system is able to reach full pressure and stay there for a sufficient number of miles, it won't allow the mechanic to even run the test. And that's what happened to you, Srikant.

While you can fail the readiness test because of an actual leak (or a loose gas cap), it's more often caused by not enough driving. That's what your mechanic thinks it is, and he's probably right.

So, here's the solution: Fill up the tank, and make sure the gas cap is properly secured. Then pick a nice restaurant about 40 or 50 miles from home. Take your wife there and have a wonderful lunch.

Get a small box of pastries to go, drive right back to the inspection shop, give the pastries to the mechanic and ask for another test. With 80-100 miles driven on the same tank of gas over a short period of time, you should pass with flying colors, Srikant. The pastries are just an insurance policy.

And if it works, call the restaurant and make another reservation for the same day next year.

When it’s time to say goodbye to your old car, here’s the perfect solution: Donate it to your favorite NPR station. They’ll even pick it up at your convenience. Here's how.