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98 ford ranger 4.0

fuel running lean…how do you adjust it??

Scan for codes. Check the fuel pressure. The diagnostic tree should walk you through to the proper repair.

You can’t adjust the fuel/air mixture, you don’t have a carburetor. Your problem is fixed essentially by a part or parts change.
You should see the CEL on, and if you check the codes they should indicate PO171 and/or PO174. You can have the codes checked for you at any Autozone or Advanced Auto Parts stores. Ask for the codes themselves, not the description - you want the codes in case they differ with the ones I’ve cited. You can look up any different codes online.
If the problem does involve the codes I’ve cited, before you do anything else, first clean the MAF sensor, and replace it if cleaning doesn’t help. I can’t do as good a job as this site to tell and show you how and what to do:
Unfortunately, Ford apparently decided to use a special fastener to hold this very stationary part in place, which means you will need to go buy a new tool, “a Torx Bit T20 screwdriver” to remove the sensor. I know that sounds like bs (it is, too: any fastener at all would hold this part in place forever) but you should start with buying the tool. The part is located on your air filter housing, by the way. Look at the picture provided in the site and find the air filter housing in your engine compartment and match up. Hopefully just cleaning the MAF sensor will fix the problem. Notice that the site even includes which cleaning product to buy, which I endorse also. Don’t use anything else. Bear in mind down the road you will need to occasionally clean the MAF sensor in any event, so buying the cleaner is not a waste of money.
If cleaning the MAF sensor doesn’t correct your problem, replace the MAF sensor next. And so on. The site does a good job of minimizing work and costs to solve your problem.

Vacuum leaks and PCV issues are also common causes of lean codes. I would definitely check that possibility out before replacing the mass airflow sensor. Cleaning the MAF sensor is a good place to start, but a mass airflow sensor is an awfully expensive part to throw at the problem, hoping to solve it.

If you do try disassembling the mass airflow sensor to clean it, the bit you will need is actually a tamperproof Torx T-20, which may be somewhat challenging to come by. If you like to work on stuff and have a Harbor Freight store nearby, an excellent source for the needed bit is Harbor Freight’s 100 piece bit driver set. There is no bit driver included, but it does have every kind of bit imaginable in there, including tamperproof Torx, standard Torx, flathead, Phillips head, swept Phillips head, square head, wing nut drivers, hex, spline, tamperproof hex, triangle drive bits, and some other stuff I have never even seen before. The set runs about ten bucks and you will be able to disassemble anything held together with small fasteners with it.