Lincoln/Mercury Repair: 89 Coug. wont DEcelerate., vacuum leak, vacuum line

Question
Question -
I've got an 89 Cougar that,  after driving a short distance and the engine warms up, the engine wont slow down and stays at the last rpm's when I take my foot of the gas.  When checked at the local "Auto Shop" it showed nothing irregular with the DTC's. I'm lost as where to start looking for the trouble.

Answer -
Hi JD

Does it feel like the throttle cable is sticky?

When I stop and look under the hood, The throttle is not sticking and is relaxed.  Its almost as if it's running too lean and that's the cause of the racing engine.  I can shut it off, finger the throttle back and forth. See that it's in the relaxed position, turn it back on and it still races.  The next day, it may start up without racing until I drive it on the highway.  

Answer
Hey JD,

Sheesh, I'm over worked! LOL I should have recognized this at first, you likely have a vacuum leak. The engine is over revving to compensate. Listen under the hood for a hissing sound and try to track it down. There are miles of vacuum line under the hood so I couldn't even tell you where to start unless you have another system that is acting funny. Let me know where you find the cracked or broken line.

Hey JD, What did you find?