Why is it accelerated?

That my question is about a Ford Thunderbird SC 1994 which I don't know why it stays accelerated when stopping in a semaphor, it stays in 1200 rpm approx a few seconds and then they go down to what is normal about 800-900 rpm the thing is that if I touch the accelerator a little and the RPM goes up when the same passes the same thing there are a few high seconds and then they come down.
that I can verify and as I do schere I think this is causing me other problems but I want to know first why this happens
thanks

Hello Cesxandro, an air intake to the collector I do not think you have any cuffed in the admission, because it would be accelerated all the time, but if I believe that the flow is "becoming old" and it takes already to stabilize the measure of the volume of air that enters the admission, that time, it takes to go down to its normal rpm. There they will tell you to clean it, my advice is that they cannot, nor should they be cleaned, because they already do it for themselves, in addition to it is a very sensitive piece. greetings

2Tambien, apart from the flow of the flow, it can be a problem of gasoline pressure on the ramp, that when deceleras, it takes to descend the pressure and enriches the mixture accelerating the regime until it stabilizes and lowers around, these two responses I think they can guide you, to discard, it measures the pressure in injection ramp to the idle These change the regulator. Problems, because I do not think it brings you any important, the only thing you have a little more consumption.

Hello!
For me, the problem concentrates the step by step, idle valve, or another name that is usually given by.
This valve mechanically regulates the air entry into the combustion mixture, and when we wear out, it takes longer to react, which produces a longer acceleration when the accelerator pedal releases, until it manages to calibrate, and it takes the idle to the optimal rpm.
Sometimes they usually respond well to a "reset": disconnect the battery for a few minutes, and then plug it back. If this does not work, change the valve.
Luck!