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Q: Hissing sound

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Q: Hissing sound asked by Jimmy F on August 23, 2016

Hello, on my two cars Hyundai i10 2010 and BMW x3 2006 I can hear a hissing sound when I open the throttle On the Hyundai it can be heard on low RPMs and it sounds like a vanos valve(which I doubt that car has) but on the X3 it is much higher and can be heard at high RPMs (Full throttle).

Follow Up Info: No check engine light on yet at full throttle a burn odor can be smelled. Are these two things correlated?

My car has an automatic transmission.

A: Hissing noises when the throttle is opene...

Hello.

Hissing noises when the throttle is opened can be considered normal. If the hissing noise is excessively loud, or can be heard when the throttle is closed then that may be a sign of another issue, perhaps a vacuum leak. A burning smell can be caused by a few things, commonly by oil or power steering fluid leaks that make contact with the exhaust manifolds. I would recommend having the vehicle inspected by a certified mechanic, like one from YourMechanic, for any leaks, and checked for the hissing sound, to see if it is normal or perhaps related to the issue.

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