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Hi there, Your problem is most likely your IAC, (Idle Air Control.) It's mounted directly to the throttle body with a wire conector plugged into it, and attaches with two fasteners. I have a 1993 3.8 T-bird LX, they both use the same part for idle control. When mine went bad, the car would start fine and immedatley go up to 2000 RPM and hold there, and then the noise started, very disturbing. Your description of a jet eninge is pretty close, and it will make that sound as the engine turns off. The IAC has a bellows in it that pulls or pushes the valve onto or off of the valve seat to control the flow of by pass air at idle. This is how your cars computer maintains your idle. When the throttle blade is closed at idle, this valve can pull in some air to raise it, or restrict air to lower the idle. What has happend is the bellows has worn out and has a hole it, so the air rushes in and cannot be controlled to maintain the correct idle. The sound is the air cavitating the bellows, and is then amplified by the air intake tube that connects from the air box to the throttle body. Just replace the IAC, and everything will return to normal. Look on the net for Ford replacement parts and shop the price around until you find what you want. Hope you have success in fixing this one yourself and saving on the cost of having it installed at a dealer, ouch. NOTE: To remove, Unplug the wire connector,loosen the two fasteners atop the IAC, should be 8mm or 10mm, I'm going off memory here. Pull the IAC off the throttle body by lifting up. Clean the gasket surface if the old gasket sticks on there. Put new gasket, (included with part purchase), under the new IAC. Re-install the two fasteners and hand tighten. Plug in the wire connector, and your done. Now start your car and listen to the sweet sound of a super coupe at the correct idle. Good job, you saved yourself a bundle on that repair, and your car is fixed.

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17y ago
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Q: Your 1989 tbird sc idels at 3000 RPM and make a awful noise when shut down sounds like a jet landing?
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