2000 Ka - over revving when engin heats

I'm sure this topic has come up before. My 2000 model Ford Ka with 1.3 lt engin does this strange thing where the revs seem to maintain even if I let go of the accelerator. This only happens when then engin is
hot. As I hit the brakes, the revving slows down back to normal when the car comes to a stop, regardless of clutch position or whichever gear I am in. I have taken it in to Ford before to have this problem fixed, and they ran another wire from somewhere to somewhere, I think it might be from the inlet manifold sensor to the computer?? Not sure. They told me that when the engin heats up, the electrical resistance on the wire (fitted at factory) is a lot higher and small electrical signals are not getting from the sensor to the computer properly - causing malfunction, ie over revving. Adding this new wire stopped the problem temporarily, but now it has come back again. Any suggestions from anyone would be greatly welcomed? I have been told I would need to replace the entire inlet manifold with sensors and all. I somehow think that this will cost a lot. Thanks, Dan.
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Replacing the intake manifold will be expensive. I would try replacing the wire again. Perhaps the connections have become corroded, increasing the resistance. If that doesn't work, it seems it wold be cheaper to replace the one bad sensor than the entire intake.
The Ford Contour has a unique feature in that when you push in the clutch, the revs stay up for a few seconds and slowly go down over a few seconds. This is to help prevent a bunch of unburned hydrocarbons or other pollutants from exiting the engine. This is what first came to mind, but it seems that if your symptoms went away, this is not the explainaton.
Jeff

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