Couple weeks ago my truck would stall out when the engine was cold at idle. Would resolve itself after warming.up. Then yesterday the battery.light would turn on like it was ready to stall at idle but not stall. Then yesterday it would not start. I have not run any codes. Any advice would be welcome.

150,000k miles,

 

Advice , maybe, suggestions ,yes.
If you have any carb/choke cleaner available (closest to gasoline) and sprayed a shot or two into the air cleaner, will the engine start or attempt to start? If it does it would confirm a possible fuel supply problem. The better way to do this is to get hold of a fuel pressure gauge and see what kind of fuel pressure it has when cranking.
Depending on the results there, will determine where we go from there.

 

I don't think I can do that because the engine was not cranking when it died. I was going to try to clean out/replace egr valve and fuel filter.

I don't think it's electrical because I just changed alternator, plug, o2 sensor.

 

So we are on the same page.
Cranking is what the engine is doing before it starts to fire up and run.
You could be right, but it could still be electrical and here is why I say that.
If your diagnosis was correct and it needed an alternator, it is possible the engine just died because the battery was completely drained of power.If possible a jump start may help to get it started.

An EGR vale that may be stuck partially open can cause idle problems both cold and hot. What you are doing can't hurt and could help solve the problem. If it does not, maybe we can offer some addl items for you to check..

 

So it looks like the problem was electrical. Eventhough the alternator was replaced by me a year ago.

The stock alternator is 95 amps but they make one that is 130 amps, but it says.it will fit 2000 ranger 4.0 automatic. (My truck is 3.0 manual) Was wondering if anyone has tried this?

 

you should repair it.

 

The vehicle manufacturer equips a vehicle with the output required from the alternator to put the energy back in from starting and operate the vehicle supposedly under all operating conditions (electrical load).
An increased output alternator will put out more current if required without overheating, but if the wiring on the vehicle is not built to handle that increased current , it can cause problems, among which are fried wires from the alt to the battery and or power supply to the vehicle.If components are added that require higher current, the wiring should be made sure can handle the increased load.