I hear a metalic clicking noise when i step on my gas pedal, why

Try some higher octane gas. When fuel tank is empty.

bad coil

Most automatics have a lock on the transmission selector.
When the vehicle is in P (Park) you are not able to select drive or a gear unless you depress the brake pedal.
My Audi Q7 ha a solenoid and you hear it click when I put my foot on the brake.
This solenoid stops you from accidentally selecting a gear without the brake depressed.

Is it a single click when you depress the pedal.
Or is it a constant click click click ?

Do you hear the noise when pushing the clutch pedal? Bad throw out bearing. Hear the noise while moving could be in the transmission or the rear differential. Drain the oil out of both and look for metallic flakes in the oil. Shine a bright light on it as I am sure it will be black.

if you are getting a grinding sound or feeling then your brakes lining is gone and you are down to the metal. you need to fix this asap the longer you drive and use the brakes the more damage you are doing to the rotors.

I worked at a trans shop as a rebuilder for 7 years. That code can only be fixed by replacing the torque converter. The noise is related. The stator and turbine clutches in the converter have come apart causing it not to lock up therefore causing the po740 code.

When you say the work clicking I think of CV axles going bad. But you would mostly hear this when turning the car. A cracked exhaust manifold will make a ticking noise when the cylinder fires where the crack or leak is. It will be louder when cold as the metal will shrink when colder then expand and close in the crack when hot. If the power really is cutting out when you hear the clicking then it could be an arcing plug wire or plug but this would throw a trouble code for a misfire.

Hello tgiro7: My name is Roger and I will help with your question. The fact the noise goes away when stepping on the brake pedal says the problem most likely is in the brake area. The pads could be worn out even at 20,000 miles.If the noise sounds like it comes from the front remove the wheels and check the front pads. If the pads are bad most likely the rotors are also bad.Same would apply if the noise emits from the rear. When you have the wheels off check to make sure the calipers will slide in and out on the mount pins. Should they be stuck on binding the pads will wear excessively and prematurely fail. The calipers must move freely on the pins. If you drive with your left foot on the brake pedal? The amount of pressure required to apply the brakes and not stop the vehicle is 1 to 2 pounds of pressure. Wont turn on the brake lights but will put pressure on the calipers. This in turn will wear out the brake pads. Another thing to look at would be an out of adjustment brake switch. Reach down and grab hold of the brake pedal. Give a firm tug on the pedal. Should you feel the pedal give and hear a click or two the switch was set to deep and holding the brakes on.
Should you need further help please just ask. Please rate the answer. Thank You for using Fix Ya. Roger

Is this almost like a metallic buzzing sound?

Find the catalytic converter under the car it should have a shield on it. Use a broomstick with the car running and hold the shield still and have someone give it a little gas. Just move from shield to shield until you find the offending shield.

Don't touch these with your hand as they can get hot fast.

Most parts houses sell a very large hose clamp to go around these shield for about $10, they will know exactly what you are looking for.

HAVE THE DRIVESHAFT UNIVERSAL JOINTS CHECKED FOR EXCESSIVE WEAR, THEY CAN MAKE THIS TYPE OF NOISE.