Engine lacks power/sluggish top-end
I have a 1987 4x4 Ford Ranger with 5 speed tranny and the ever so loved 2.9 liter engine with 33" tires....The truck has been running fine for the last two or so years until recently,,,I've noticed will going up a hill that I have a significant loss of power....I mean I can push the pedal to the floor and have no acceleration what so ever.....So I began testing it out and come to find out if I am traveling along 55 or so and floor it it has very little to almost no acceleration capbility. It seems to lack top-end power all together.
I have started a troubleshooting process of elimination to find a cure for this problem but have had no sucess....I have done a basic routine maintenance tune up with new spark plugs, oil change, air filter, etc.... I have replaced the fuel pressure regulator, both of the fuel filters and the fuel sending pump within the gas tank.....BUT I still have the sluggish problem.. Somehow it only seems to do this under loading conditions though.. The reason why I say this is I can be going up a hill with it floored and it losing ground speed substantially but if I push in the clutch with it floored the engine revs up with no problems... this leads me to believe it could be some other problem than the engine...I'm not sure though....If anyone has any ideas I am open to suggestions.....Thanks..