The “ten pin” connectors are these salt and pepper shaker looking things found at the back of 5.0L engines -between the intake manifold and firewall. These connectors are notorious for developing poor connections and causing strange EEC quirks, like idle fluctuations, intermittent drivability problems, and unexplainable diagnostic codes to be triggered.

 

Ford issued recall 91E19 on 3/27/1992 just for this problem, and created an “extension harness”, assuming the original harness was too short causing the large connectors to pull apart. The real cure for this problem is cleaning and re-shaping the electrical terminals inside the connectors. You should consider doing this as preventative maintenance even if you don't have problems yet.

 

Always start by checking the basics: computer diagnostic codes, vacuum leaks, fuel pressure, Cap & Rotor, Plug wires & spark plugs.

Disconnect the negative battery cable! To open the connectors squeeze the four side clips and pull apart. Do not pry the clips apart as with other connectors. Inside you will find ten male and female terminals.
 
 
 
 
 
 

First use a small pick to slightly squeeze the female terminals closed.
 
 
 
 
 
 
 
 
 
 
 

Then spread the male terminals open just slightly. This will ensure a complete electrical contact.
 
 
 
 
 
 
 
 
 

Before reassembly take some spray electrical contact cleaner and clean the male and female connectors. Then fill the female terminals with dielectric grease to prevent corrosion.
 
 
 
 
 
 
 
 
 
 

This problem is not isolated to the salt and pepper 10-pin connectors. The EGR sensor has a history of this problem, and many other Ford connectors. This is a regular maintenance repair you should plan on doing to your aging high mileage Ford.