Just swapped a 2.3 & T5 from a 87 mustang into my 87 ranger .When you first start it up it idles fine after about 5 mins the idle picks up all at once to about 900 + rpms.If you shut it off it will idle fine for about 10 sec and idle up again.Im thinking maybe a bad sensor.Any ideas? THANX!

 

Could it be running in the closed loop then when it gets up to temp its opens and is getting a false reading from a sensor ?I noticed the temp & oil pressure gauges are not working also could this be a factor? THANX!

 

Changed it and working GREAT!