Mazda CX-7 makes unknown noise on cold start

Not long ago, there was a problem with the car engine, so I paid a total of $7,000 to replace the engine. They said there was a six-month warranty. But I hear an unknown noise when I turn on the cold engine. If you turn up the volume, you'll hear it well (the actual sound sounds like there's a real problem). So I asked them, and they said it was a spark plug? (Sorry im not good at english so it’s not accurate) I paid $150 to replace it. But the sound seems to be louder and longer. They're avoiding repairs, saying there's no problem driving (they can't even find what's wrong), but maybe you guys know what's wrong with this?
 

Attachments

  • trim.024F2825-8E1D-4AA7-8F1E-CFD1AB3E2B6D.MOV
    6.6 MB
Last edited by a moderator:
Back