Very low idle when comming to stop

My 94 Passport 2.6 has been having a problem with the idle when coming to a stop with the clutch in and off the accelerator it will idle rough somewhere aroung 400-500 rpm maybe lower but once the truck comes to a complete stop the idle will come up to 1000 rpm QUESTION: is there any kind of sensors in the tranny or on the wheels that I can check? only reason I ask that is it only idles rough when rolling to a stop other than that it idles fine.

any ideas???

Ground wires for the Injectors were loose, now it is running strong.