Drive it forever

Q: My minivan has failed to start a couple of times recently because of a low battery. It turns over but it won't spin fast enough to catch. My mechanic says he tested the battery and it is bad. But it is only a year old. I checked the voltage at idle, and it is 13.8 volts. All of the cells have plenty of water. I think it is something else.

A: There is more to checking a battery than testing the voltage and looking inside for low water. For one thing, you need to check the voltage when the engine is turned off, not when the alternator is raising system voltage to its normal level. You can test for proper cranking voltage with a voltmeter while - you guessed it - cranking the engine. The several hundred amperes of current the starter motor draws should pull the battery voltage down to a normal nine to 10 volts. Do this test: Disable the ignition or injection to prevent the engine from starting. Then put a voltmeter across the battery posts while cranking it with the key or an external remote starter button. Crank for 15 seconds (no longer); the battery voltage should remain 9.6 volts or above. (These are General Motors specifications for a battery at 70 F; your mileage may vary.) Another way to check is with a dedicated battery tester that has its own internal resistor pack and voltmeter. This is a lot easier to use - you don't need to disable the engine to crank it. Just check the voltage after 15 seconds.

Q: My 1998 Corvette is able to pass its California smog test, but it barely passes Nox (oxides of nitrogen) at 15 miles per hour. It is good at 25 miles per hour and all other tests look good. I am using 89 octane fuel. Will the 15 miles per hour Nox level improve if I were to use 92 octane instead of an 87 octane gasoline?

A: No. You should check for proper exhaust gas recirculation (EGR) function; it may be partially blocked by carbon.

Q: I have a 1988 Honda Dream 125 motorcycle that I bought used. I live in Thailand and I want to bring it back to the United States. I have been told it won't pass emissions inspection. Is this true?

A: I'm pretty sure there are no emission requirements for 1988 motorcycles. You should check with the US Environmental Protection Agency. And if you're going to California, you should check with the California Air Resources Board as well.

Q: I own a 1995 Oldsmobile Aurora (it has a 4.0-liter V8 DOHC engine and front-wheel drive). At around 65 to 75 miles per hour I experience a vibration on the steering wheel, but mostly on the car. I installed new rack and pinion inner and outer tie rods, ball joints on both sides, lower arm control bushings, rotors, and pads, front struts and rear shocks, and had a four-wheel alignment. However, I continue to experience the vibration. The motor and transmission mounts seem to be fine (there is not a lot of movement on the engine when I put it in gear). The wheel bearings also seem to be OK. Do you have any suggestions on what the problem is?

A: Out-of-round tires. And not necessarily the front tires.

Q: I have the Popular Mechanics auto repair CD-ROMs that I bought several years ago. I tried to add more data to my GM repair file, but the source is no longer in existence. Is there another site I should go to, or do I just start over?

A: Popular Mechanics, in partnership with ALLDATA, used to market CD-ROMS with repair information. This product has not been on the market for six or seven years, but apparently there are a few still in use. ALLDATA now provides this repair information at: alldatadiy.com.

Mike Allen is a senior editor for Popular Mechanics magazine. Questions should be sent via e-mail to driveit@nytimes.com.