This time, let’s start out by dispelling a myth. You have a dirty air filter and a lot of technicians tell you that that dirty air filter will cost you a lot of money because it decreases fuel economy. Well back in the day that was true. Back when we had carburetors.Today, not so much.

See the reason is the air filter sits up here. Air comes through the filter into this tube, through the tube and down here to the throttle body.

Now the throttle body typically also has what is called a mass air sensor in it. And that measures the amount of air coming into the engine. Now the way all of this works when you step on the accelerator inside the car, this butterfly or flap inside the throttle body opens up. It allows more air to come in. The computer senses the amount of air coming in the engine and it mixes the proper amount of fuel with that air.

So, if we have a dirty air filter and it reduces the amount of air coming into the engine- what’s going to happen? Well, the computer is going to sense that there’s less air coming into the engine. It’s going to mix the proper amount of fuel with it so that the ratio of fuel to air remains the same. And therefore the fuel economy doesn’t decrease. Now granted if the filter is completely clogged up, yeah, it might, but the car will probably run at the same time.

Alright now, here’s the thing with throttle bodies. Number one, they get dirty over time. We can see the difference between the two of these. And when they get dirty, different things might happen.

Number one, you may have a throttle that when you step on it, the car lurches or it doesn’t idle right or something like that. Well, you have to keep throttle bodies clean. And to do that you need to have the proper chemical. You can’t use the old carburetor cleaner because that could damage parts in here.

Also, if you're going to clean the throttle body and the mass air flow sensor you’re going to need a dedicated throttle body cleaner and mass air flow cleaner.

Now the big thing here is to learn the procedure. Don’t just go prying on this throttle body to open it up so that you can spray the cleaner in there. There are special procedures for various cars and if you don’t do it right, you could be buying a new throttle body. So this could save you a lot of money at the repair shop if you learn how to do it and if you do it right.

And if you have a question or comment, drop me a line right here at MotorWeek.