I have an 88 auto, on the interstate it has been seeming to not have much power, I have a hard time keeping it in overdrive, and it seems to want to lose speed. It also wanted to "buck" or sputter at about that 55 mph shift to OD. Anytime (on the interstate) when I would even drive up even "not so big" hills I would lose at least 15+ mph. I put on a new cap and rotor and wires thinking it might be missing. It ran alittle better, but still does all the same things. I have run injector cleaner through the tank, with little or no improvement. Today I checked the fuel pressure, thinking it may be a regulator, and it held steady at 30 lbs. even after I shut it off. When I revved it, it went to about 37 or 38. Then I changed the fuel filter. The gas that came out of the fuel filter was very dirty and blackish looking, (pooring it out from either side, dirty and black) tested pressure. Still at 30 and 37 on revving. took it for a test drive and still lacks the power. If I accelerate at basically full throttle or close to it, it will occasionally, un-sputter and accelerate decently quickly, before bogging back down. My question is do you think it might be the fuel pressure regulator or one of the pumps, and if so, then which pump? p.s. I dont notice any black smoke upon start up, but it has been getting bad gas mileage also. When idling it runs decent with an occasional stumble every 15 or 20 seconds)

 

Have you been able to leave the fuel pressure gauge on while you drive it? At this point, the fuel pressure numbers don't suggest anything wrong with the fuel system.

It may or may not be the case, but I remember one trip when my BII behaved a lot like that. Upon inspection, I found that the distributor hold down bolt had come loose, allowing the distributor to wobble about. Reset the timing and tighten the distributor down and everything was fine.

 

Have you looked at the vacuum lines? I am only asking because I had a problem with an intermittent loss of power with my '87 2.9 5 speed. Mine almost died on me while accelerating to blend in with traffic but that wasn't the only problem. I did have an issue with the fuel regulator too and like you my fuel filter was dirty. The electronic throttle controller was replaced as well.

Also are you the original owner? The previous owner of my bronco II put a darn chip in it and it had some sort of fail safe which would cut fuel off when the motor was cold while accelerating, it was very annoying. So I had to have the chip tuned down so to speak. I doubt you have that going on though.

After all these things were done I haven't had the problem since. The truck has treated me very well, I do have the little sluggishness when the motor isn't warmed yet up during the cold mornings but it quickly goes away within a minute or two.