Dear Jim,

I have a 1998 Ford F-150 pickup (4.6L, V8) and it's been great ever since I bought it. It's got about 88,000 miles on it, and I'm the original owner. I've never had any serious work done on this truck, just tune-ups and oil changes, but the "check engine" light came on a few days ago. There doesn't seem to be anything wrong because everything else is normal. Do you know what this could be? Should I stop driving the truck while the light is on?

-- Tim Kohler

Sounds like you bought a solid vehicle, bro. As for the engine light coming on, well, that's not uncommon. In theory, it could mean a lot of things. You've only had to get tune-ups and oil changes, though, so if it were something serious, you'd probably know it by how the truck is driving. With that kind of mileage on the truck, chances are you have one or more bad oxygen sensors that need to be replaced.

The job of these things is to measure oxygen levels in the exhaust coming from the engine, and then feed that information to the vehicle's computer. The computer can then figure out what kind of air/fuel mixture exists in the engine and adjust it to get the best possible balance. If the air/fuel mix is rich (too much gasoline) or lean (too much oxygen), then a vehicle's fuel efficiency can be knocked down quite a bit. Poor engine performance can result, as well as excessive pollution. Based on what the oxygen sensors tell it, the computer can adjust that mixture and make it "perfect" for the best performance.

Your truck should have four sensors: two before the catalytic converter and two after. Have them all checked. The odds are good that at least one of them can't do its job anymore. Once the necessary replacements are made, the computer can be reset and the engine light should go off. If for some reason it doesn't, bro, you may have to look elsewhere for the problem -- sometimes it's simply a "check engine" light that won't go off.

Tip of the Week:

Some of you will be heading up to colder locations such as Mount Charleston or Brian Head soon, and you never know when you might hit some precipitation. Old, cracked windshield wiper blades won't do the job, and that can be dangerous. Check those blades and replace them if they're looking ragged.

Buffalo Jim, owner of Allstate Auto & Marine Repair in Las Vegas, writes a weekly column. Send your automotive questions to him at buffalojim@lasvegasniftynickel.com. If Jim picks your question to answer in Nuts & Bolts, you'll also be the proud recipient of a deck of official Buffalo Jim playing cards, presented in a classy, tin box bearing his hairy image.