Every time i start the car when its cold the car has a popping sound at idle.(Seems like its comming out of the left tailpipe) Iff i rev it alittle bit and let off it really backfires, and its not a good sounding backfire eithor. But when the car warms up it goes away. It seems like its getting progressivly worse. Is this a tunning issue??? , can a bad 02 sensor cause this. Any opinions would be highly appreciated..
Thanks
Ryan

 

Could be timing, exhaust leak, tuning, too much fuel not being burned. Just some ideas for you.