Help!! I have a 2006 Mazda 6. It has a problem and I have no idea what's going on...the car starts just fine. Idles normal. I press the gas and nothing. Rpms don't move. I hit the brake and it dies. It also makes a weird crackle noise I just got it out of the shop. When I put it in the shop it was running rough. It threw a code that said there was a misfire in cylinder 3. Mechanic changed all 6 plugs and all 6 wires. When we picked it up he told us the catalytic converter was clogged and that's why it wasn't running any better. So we took it to the exhaust shop and they cut 2 converters off and replaced with a pipe ( he said he called a Mazda dealership and this would be fine) the car ran a little better that day but still something was not right. We drove a couple more times before it completely lost all power. Any ideas where to start?

 

Strange behavior.