I have a 94 <NOBR style="COLOR: darkgreen; FONT-SIZE: 100%; FONT-WEIGHT: normal" id=itxt_nobr_0_0>Ranger</NOBR> V6 4.0L that is going through about a tank every two days. Only codes that were there was a
157- MAF sensor went below 0.4 volts during the last 80 warm-up cycles. AND
998- Hard Fault present.

Whats this mean exactly? Any help with these will be greatly appreciated.

 

998 just means the PCM is in limp home mode.

Fix the 157 & 998 will go away.

You need to test the output of the MAF sensor & see if it tracks as you increase the RPM's.

I have an Actron CP-9087 that will test the output of a MAF (& other sensors) in couple of seconds.

 

Well, a 998 code could mean you are not running the key off key on test correctly. That might explain why it a "hard Fault" rather than a component failure. Take a look at a web site called "the ranger station". Look under their tech section. There is also a tip on cleaning the throttle body.