ok guys i know there are other posts about this but i thought i should share my experience. My brother in law has a 1991 bronco, 4.9L, 5 speed and it started running rough, surging for 5 minutes on a cold start up, on the days it would actually start. He took it to a shop and they put a new Idle Air Control valve on it and it ran good for a week. I had put new fuel and air filters, spark plugs, wires, cap and rotor on it and replaced the throttle body gasket as it was causing a huge vacuum leak. It would run strong and then one day no start. Sometimes the fuel pump would run constantly and sometimes it would shut off after its initial 5-8 second start up sequence. If the fuel pressure regulator does not have good vacuum to it, the fuel will not energize the injectors. It will just bypass it back to the fuel tank. Thats what i was heaing somethimes. It actually decided to start yesterday and once it did its idle surging fit and warmed up i pulled the vacuum line off of the fuel pressure regulator. There was hardly any vacuum at all!!! I shut it off, replaced the tiny plastic line with a larger vacuum hose and when i turned the key the fuel pressure energized the injectors, shut off and it fired up the fastest i have ever seen it. Now it idles perfectly every time and it has tons of power. I was actually able to chirp the 33's on it as i shifted into second. Im sorry if this is too long but i hope you can enjoy my victory too. Dale

 

i think i will try that also since my fuel pressure tester is still hooked up and see if theres and pressure changes

 

yeah man after years of exposure to under the hood heat, alot of the little plastic vacuum lines get cracked and leak. I had spent almost an hour with a can of carb cleaner spraying it on every vacuum line to find leaks. I replaced 4 other lines and the fuel pressure regulator didnt leak on me, but it wasn't allowing the vacuum to pass. Weird huh? It sure beats having to replace a fuel pump.