So I have a 2016 lancer, it has about 65000 miles on it. I got it used and now it’s making a rattling sound as well as when my wife and I are driving it it will sometimes chug and blow some white or blue (can’t tell because of the tint) from the tail pipe. I took it to an auto shop which they couldn’t tell me what’s wrong. And the computer I have isn’t pulling any codes. Also the rattling sound is only when driving and it’s either under the car or from the engine bay. Please help

  • without more info this will be tricky. Can you get someone else to look at the smoke to see what colour? And describe the rattling - does it change with revs, or with road speed?
    – Rory Alsop
    Feb 19 '20 at 11:14
  • take the car to an other mechanic and ask him to take the car for a test drive,blue smoke=oil burning what is the oil level.white smoke=water what is the cooling fluid level in the reservoir/radiator. Feb 19 '20 at 11:22

I would check the noise first, I broken catalyst will show all those symptoms, and to diagnose it if it sounds like it is coming from inside the cat; hit the outside hard with hammer. The dent will stop the rattling for awhile. I always check for blown head gasket,vacuum leaks, fuel trims. there is usually something that killed the cat, it might have been repaired already,might not be repaired and will kill your next too.

  • A hammer blow could also smash the catalytic converter. An expensive mistake.
    – HandyHowie
    Feb 19 '20 at 12:57
  • If it is already rattling and blowing smoke it is failing. You can check pre and post o2 sensor and see performance degradation. You can also test back pressure but I don't recommend that to novice, that is something were it is to easy to test wrong to get the answer you think you are going to get . Feb 19 '20 at 13:03
  • Maybe the information in your comment would be better added to your answer.
    – HandyHowie
    Feb 19 '20 at 13:20
  • @JoshuaEcvHaislip nothing in the question point to a broken cat so to whack the cat is realy a bad idea and an expensive one. Feb 19 '20 at 14:29

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