Click and Clack --- Tom & Ray Magliozzi: Pre-stomp on pedal doesn't matter

Tom and Ray Magliozzi's auto repair column appears Thursdays and Fridays in the Sun. Got a questionabout cars? E-mail them by visiting the Car Talk section of cars.com.

Can you please say something about fuel injection and the need for being careful NOT to step on the gas before starting up the car? Why don't dealers impress this upon customers who buy fuel injected cars these days? -- Dorothy

Tom: Mostly because it doesn't matter, Dorothy. In the old days, when my brother had hair and Dodge Darts roamed the Earth, you HAD TO step on the gas before starting a cold car to set the choke. But since cars don't have chokes anymore that's no longer necessary.

Ray: Cars are now fuel injected and controlled by computerized engine-management systems, which read the engine temperature, and in some cases the ambient air temperature, and then determine how much fuel and air to send into the cylinder when you turn the ignition key.

Tom: And these computers couldn't care less if you step on the gas pedal before you start up. As long as your foot is not on the pedal while you're turning the key any such "pre-stomping" will have no effect whatsoever.

Ray: But you do have a point when it comes to stepping on the gas pedal WHILE you're starting the car. While stepping partway down on the gas doesn't do any damage to the car it does make some cars start more slowly. That's because you may be opening the throttle slightly when the computer wants it closed. Again, no damage is done, but it's completely unnecessary and may make starting the car harder.

Tom: Another reason to get out of the habit of stepping on the gas WHILE you start the car is that as soon as the car starts it's going to rev up. And we know that revving up a stone-cold engine as soon as you start it is one of the worst things you can do.

Ray: The other thing you should be careful not to do is related to what's called a "W-O-T mode."

Tom: Oh, my Dodge Dart was in W-O-T mode last year. With-Out Transmission!

Ray: No. W-O-T stands for "wide-open throttle." In the old days, when my brother had brain cells and the Earth's crust was still warm, carbureted cars had a mode for starting the car when the engine was flooded. You held the pedal all the way to the floor while you turned the key. That opened the throttle all the way and let in the maximum amount of air to counteract the excess gasoline.

Tom: And most car's computers are designed to "mimic" that W-O-T mode. So if you hold the gas pedal to the floor while turning the key the computer assumes the engine is flooded and cuts the supply of gasoline in half. So that's something you want to be careful not to do by accident.

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