i dont know how many miles is on your truck but between 75-100,000 you should consider a full tune up but here are some cheaper tips,
1. if water is in the gas they sell additives at part stores dont get the cheapest one quality matters here i worked at a parts store for years before the navy ive tried plenty of different ones usually the more expensive the better
2. seafoam is an additive for gas, crankcase, or even transmission. look it up on youtube its effective and has many uses the best use is taking the vacuum tube off of your brake booster and pouring the seafoam down the tube while your vehicle is at idle there are instructions on youtube specifically for rangers. pour anything from 1/3 can to full can. the next best thing for seafoam is simply putting it in your gas tank before fill up so when you fill it up it mixes well.
3. check all of your vacuum tubes for cracks or even if they are just not there.