I've been screwing around trying fix my idle surge and terrible gas milage for quite a while now. I was getting an EGR code and a Running Rich code. Without much thought, I replaced the EGR valve and the O2 Sensor. The problem did not go away. After reading a few posts (from UncleDon and Taylor). I realized that it could be a fuel pressure problem. I bought a Fuel Pressure Gauge and a book that tells you everything you want to know about the Ford EEC IV System (it's a great book and is available on Amazon.com). I've learned a lot from this book. After reading the book, I tested the fuel pressure: It was about 40psi with Key On Engine Off (within spec), but when I started the engine, the Pressure Pinned the gauge (indicating a bad Fuel Pressure Regulator). I replaced the Regulator (very painful to remove those 3 screws) and EUREKA, the idle problem is gone! I highly recommend buying a fuel pressure gauge, vacuum gauge/pump, and this EEC IV Book for understanding how to diagnose and repair Broncos. Thanks for the help, guys.

That's great! And I'll get ahold of that Exxon Tanker captain by radio, and tell him we can now do with one less shipload of oil! :-)

I have this same problem with mine it's a 86 302/efi, could this Bronco fit the problem you described. Im not real good with efi stuff.

Yes. If you have an EFI vehicle with a rough idle when warm and terrible fuel economy, you should check your fuel pressure. You can buy a gauge at your local auto parts store. Look for a Shrader Valve on the Fuel Rail. Remove the cap (just like on a tire) and screw the Fuel Pressure Gauge onto the valve. Turn the key without starting the engine: Pressure should read about 39psi and it should hold the pressure. Then, start the engine. Your gauge should now read about 30psi while the engine is idling. In my case, the pressure was over 100psi indicating a bad Fuel Pressure Regulator (costs about 15 buck). Good luck.