Ford Repair: 1987 ford ranger idleing problems, throttle position sensor, air control valve

Question
I have a 1987 ford ranger. It started idling high and low and running rough, would start bucking a little. I changed the distributor, reset timing, about a week later started doing it again. Thought I had a bad distributor so went and got another new one. Well the problem is back, in about a week again. I checked the timing belt it looks fine. Do you have any suggestions to what I should check or do next.  Thank you. Bill

Answer
Bill, what temperature is the truck running at?  If the gage is showing that the truck is running well below 190, this may cause the problem.  Now, what I would do is, when the truck starts acting up, I would start to disconnect the sensors.  I would start with the Throttle Position Sensor. Disconnect this sensor.  The truck should begin to idle very wildly, or it should try to die.  If it doesn't do anything when you disconnect the sensor, then I would replace it.  I would then disconnect the Idle Air Control Valve.  The same effect would happen.  I would then disconnect the temperature sensor.  The same effect should happen.  Then I would try the EGR Valve Solenoid, not to be confused with the EGR Valve.  The solenoid is the electrical portion that sends a signal to the computer.  Try this out, and let me know what comes of it.  Jason