My kid has been working on his '87 Bronco II, 2.9l automatic. I'm trying to help, but I'm currently 1400 miles from the truck.
Started out looking for the fuel filter as the first step in diagnosing an intermittent surge. The truck is new to him, so I suggested the fuel filter as the first step. In trying to find the filter, he unhooked the high pressure fuel pump on accident. Of course then the truck wouldn't start. He hunted around and found the unhooked wire, reattached it and the truck started up. But then, it wouldn't shut off! Turning the key off killed all the gauges, the a/c, and the radio, but not the truck. He kept fooling with it and started fooling with the EEC relay. Pulled the relay while the key was in the "off" position and the truck finally died.
Now comes the odd part. If he reinstalls the relay, the truck will start but not shut off. If he removes the relay with the key in the on position, the truck continues to run. If he removes the relay with the key in the off position, the truck dies. If he tries to start it without the relay, the truck starts normally, all gauges and accessories operate normally, the truck drives fine, and shuts off when you turn the key off. What the heck?
Oh, and he drove it to work today(without the EEC relay installed)and says the intermittent surge is gone. Catch is he's not gotten around to changing the fuel filter yet. In fact the truck is just like it was when he started except he's got the EEC relay pulled out.

 

Have him disconnect the alternator. Sometimes, a diode goes bad and feeds power back into the system, keeping the motor running.

 

Worth a shot. It's been doing fine without the relay, but I've been in this business long enough not to trust it. I know something's wrong, but it's hard to visualize from this far away.