1998 Ford Ranger 4 cyl Two Wheel Drive Manual 193000 miles
All of a sudden one day while driving my 1998 Ford Ranger pickup with about 193,000 miles on it, the truck seemed to lose power when going above 55mph. It also began to almost " rumble" when you tried to accelerate. Putting the pedal to the floor you can only get the truck to go about 70mph if you're on a flat surface. Previously you could be driving 85mph and still pass someone with no problems (our speeds here on 75). Oddly, if you slowly accelarate it doesn't seem to rumble, but it will rumble if you start to go up a hill. It has a manual transmission, and pretty much cannot be driven in 5th gear because it has almost no power and rumbles when you hit the gas. However, if you put it in 4th gear you get a lot more power and it acts like it is in 5th gear. However, the rumble is still there when you accelerate. If you're driving on side streets it seems to run just fine. It feels like it's starving for gas to give it more power, but I'm no expert.
I took it in to my mechanic and he replaced the fuel filter, which he said was completely clogged. This didn't seem to help at all. He checked the catalytic converter, and he said that was fine. He also tested a few more things that showed a bunch of different pressures were fine. When he hooked it up to a computer nothing came up. I changed the air filter recently, and on reexamination that seems fine. The truck was running great before this and was previously owned by a mechanic. It seemed like theproblem occurred all-of-a-sudden. My mechanic said he doesn't think the problem will leave me stranded and that it is probably just a " tired engine" but I don't know if I'm willing to accept that answer. Everything else about this truck is great and even with the high mileage I think it has a lot more left.
Two things he suggested were changing the spark plugs (which aren't awful, but also could stand to be replaced) and the u-joints (to get rid of the rumbling, which I'm not as concerned about as just getting the power back). Could the spark plugs be what is causing the lack of power in 5th gear? Since there are 8 spark plugs (on a 4-cylinder) and it's very labor intensive on a Ford Ranger, it is going to be expensive to do that, and this truck is more or less just used to haul light loads of things from time to time. Not something I want to invest a lot of money in, but also enjoy having as a second vehicle.
Could it possibly be the fuel pump? If so, is that an expensive fix and/or worth it on a truck of this age?