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Loud Idle

5K views 9 replies 3 participants last post by  luke1983 
#1 ·
Hello,
I have a 2014 QX60 with 150k miles on it. The car has a loud idle from inside the cabin. The engine sounds kind of like an exhaust leak or a diesel engine. I get an occasional check engine light with the code P0420 Catalyst System Efficiency Below Threshold Bank1. The Catalytic converters are 1.5 years old, new O2 sensors, New Y pipe on exhaust, spark plugs 1.5 years old. My mechanic has said that the sound is not from an exhaust leak, but he is not sure where it is coming from without additional diagnostics being ran. I have also cleaned the MAF sensor, and cleaned the throttle assembly and PCV valve. If Iput my hand on the engine cover and the Air intake manifold, I can feel a vibration that matches the sound I hear in the cabin of the car. At this point, I am not sure what to check next. Does anyone have any ideas?

Thanks,
 
#3 ·
It's likely the leak is coming from the new exhaust parts. While I'm sure you have an excellent mechanic, you should get a second opinion to be sure. Engine exhaust sounds are pretty distinct.

BTW, what causes you to get new cats at 150k?
Thanks for the reply! I traded for the car and it had a bad cats the bank 1 and 2 cats were bad plus 3 of the oxygen sensors. I fixed that last year. Is it possible to have exhaust sound in the cabin but not outside? It sounds like it is right under the dash.
 
#6 ·
New plugs and coils shouldn't reduce sound unless there was a bigger issue like misfires (doesn't sound like you're vehicle has this issue).

Are your fuel lines vibrating and making sounds, where if you touch them the sound goes away? They shouldn't vibrate, given this, the fuel pump may push a slight vibration through the metal lines. It sounds like your lines are vibrating aggressively. Otherwise, the metal lines are further isolated with a rubber connection to the engine.

I'm curious about what's causing your fuel line vibration. I don't think I've helped, but please let us know if you find anything else.
 
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