My Ranger randomly drops voltage or so the gauge show, but when this voltage drop occurs it will almost kill the truck. It also has a pretty rough idle, im not sure if that has anything to do with it or not. Ive replaced the battery and stuck a volt meter to the cables and the alternator seems to be charging 13-14 volts. i replaced the maf as well to try and fix the rough idle and it helped a little for the first couple days but them went back to cutting out. most of the time its only when the truck is in gear and im stopped at a red light, but its starting to happen when im driving where its just cuts out and doesnt want to run hardly at all. i end up having to put-put around. ive been searching for an answer all over the internet and cannot seem to figure it out. Any and all help is very much appreciated!

1994 Ford Ranger 4.0
2 wheel drive automatic

 

You've probably already done this, but have you checked all the fuses? My truck did this when I had a 30 amp fuse blown in the engine compartment box.

 

I actually haven’t checked them, I just got the truck and haven’t had time but I’ll check them here in a couple of minutes.

 

UPDATE: all fuses and relays check out good

 

Welcome to the forum

12volt DC system needs a full circuit for voltage to flow, i.e. if you pull off the Negative battery terminal and try to start the engine or turn on lights nothing happens, even though everything has 12volts
This is because there is no 12volts UNLESS there is 0volts(negative) so the 12volts can "flow" THRU a device, that's what powers anything, volts must "flow" thru

So first look at the Positive side of things
The positive battery cable runs to a larger Starter Relay post, that same post should have several other wires attached, this is THE 12v power distribution post for the whole vehicle, battery 12v and alternators 13/14v BOTH share this one post to feed voltage to the vehicle
Disconnect positive cable from battery, then remove each wire from this one post and clean the ends, so they have a good bare metal connection to each other

There should be a cable on this post that runs to the engine fuse box, that's the ONLY 12v feed to ALL the fuses in the vehicle, engine bay fuse and cab fuse ALL get 12v from that one wire

There are a few Negative battery wires, the larger one should run to the engine, usually near starter motor, this is the primary 0v cable, needs to have a good bare metal connection
Smaller negative wires will run to Rad support and maybe inner fender
There is also a ground strap from engine to firewall usually on back of the head, this often gets left off after engine work, needs to be there and hooked up

And a ground strap from engine to frame, the engine and transmission sit on rubber mounts, as does the cab, so there is no ground transfer to the frame, and it needs to be grounded so tail lights and fuel pump work

Key off
A new battery should have 12.8volts
3 year old battery 12.5volts
5/6 year old battery 12.3volts and time to shop for battery sales

Engine running
Battery should show 13.5volts MINIMUM
Just after start up it can show 14.8volts, for "fast recharge" then after a few minutes it should drop to under 14volts, 13.5 to 13.8volts, about 1.1v above key off battery volts

 

Thanks for the quick responses, I will be checking those connections as soon as I get back home.

Something I left out earlier on accident is whenever it’s cuts out driving down the road I can pull over and unplug the MAF and it’ll idle really rough but drive pretty decently

it’s also has a new MAF, I just bought it 3days ago

 

Pull out the computer, its in the engine bay drivers side down low between firewall and inner fender

Your capacitors are bad, there are 3 of them, blue, at least one has leaked, under $5 to fix

Read here: https://www.ranger-forums.com/4-0l-o...a-rich-164218/

These leaking caps can cause multiple issues, no specific problems

But this would not effect voltage in the system or voltage gauge just engine operation