I recently replace spark plugs on my 05 cts, and I replaced the intake plenum gasket. After I got it put back together and started the car, there is a hissing noise. Could this be because the new gasket hasn't heated and sealed or is it something else? No difference in power or idle.
My car has 160000 miles.
My car has an automatic transmission.
This is likely due to the intake gasket not sealing correctly. I would suggest starting the car and spraying carburetor cleaner around the areas of the intake gasket (or where the leak is suspected) to see if you notice a difference in the engine idle. If the engine idle speeds up while spraying in a specific spot, it is quite likely the gasket has not sealed properly.
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