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Q: I recall being told that one should not rev the engine when first starting it because the oil has not yet reached all the components. If that is true, why do engines idle so high when you first start the car? Tapping the accelerator pedal doesn't drop the idle speed. Bowing to your wisdom.

A: During cold soak (the industry term for sitting for a while), a little bit of oil slips away from components, but not enough to result in damage when starting. A cold engine needs extra fuel because the gasoline doesn't vaporize easily. In olden days, the choke limited the air, resulting in a richer fuel mixture, and you could tap the gas pedal to release the choke and the high idle. Fuel injection maintains the proper amount of gas and engine speed. You may now kiss the ring.

Take aim

Q: I have a 2021 Subaru Outback on which the headlights are aimed too high. Isn't this a safety hazard to oncoming drivers?

A: This is a fairly common complaint. I believe the headlights can be adjusted. All you or your auto tech need is a super-long Phillips screwdriver.

Get a full set

Q: I have a 2010 Ford Fusion Sport. The tire pressure sensor fault message came on, then magically went away. I recently put on a new set of tires, and the fault message came back. My mechanic said they can hook up a device that can find a fault, but if a fault is found on one, the device can incorrectly give a fault reading on others. So, would it be best to buy a set of new sensors and replace them all?

A: The TPMS (tire pressure monitoring system) sensors for your car come as a four-pack, which costs about $50. Get them all and get peace of mind.

Quick fix

Q: I recently had the oil changed in my 2019 Hyundai Elantra GT, and when I left the dealer's service area, I noticed a "grumbling" from the engine as I accelerated to 25 or 30 mph. The sound stopped at that point. I returned to the dealer to have it checked out. The service manager told me that the "air box" had been left open, I assume during the oil change. He said that they closed it, and that it wouldn't have caused any problems. Sure enough, as I drove away, the noise was gone. I had never heard of an air box. Is it a real thing? Is it OK to drive when it's open?

A: The air box houses the air filter. It is OK to drive with it open for a while, but not all the time. Your engine doesn't like sucking in dirt.

Bob Weber is a writer, mechanic and ASE-certified Master Automobile Technician. His writing has appeared in automotive trade publications, Consumer Guide and Consumers Digest. Send automotive questions along with name and town to