Okay, here is what I'm dealing with and what I've found so far. I have a 1993 ext cab 4.0 ranger 5 spd, it's high mileage but in really good physical condition and seems to run good. I recently purchased it and it has a check engine light and code 157. Through some searching, I found that the code is for low MAF voltage. Also through some searching, I'm pretty sure the ranger has 19# injectors.

I tested voltage from A-B on the MAF at idle and got a little over 14 volts. From C-D only got 0.15 volts and it didn't fluctuate with rpm change. I happened to have the stock 19# MAF from my 1991 5.0 mustang, so I swapped it onto the ranger to see if the code would come back. Kind of suprising to me, the truck started up fine and the codes didn't come back. I swapped back to the ranger MAF and the code 157 returned. That's telling me the MAF is dead. I'd have left the mustang one on there, but it doesn't bolt up yo the air box.

What do you think, am I on the right track, bad MAF? What donor vehicles can I get one from or can I just swap the sensor guts from the mustang unit into the ranger MAF? Oh, I did try cleaning the ranger MAF with MAF cleaning spray, didn't help. What should I expect to pay for a replacement? Is there any way to test a MAF, such as ohm readings, if I find one at the salvage yard? Thanks.

It does appear to be a bad MAF.

You can get a remanufactured MAF from some parts stores, I think NAPA has them. Or you can go to a junkyard and try to find a 4.0L (OHV) Ranger/Explorer with a clean and intact MAF.

Stopped by the salvage yard and picked up a MAF from a 93 4.0 Mazda Navajoe. Put it on the ranger and all codes are gone, idle and throttle response are also improved.