So I've been pretty stumped by this for about two years now, and my friends who are better mechanics than me cant seem to think of what the issue could be either.
When it gets above roughly 70° my ranger just starts running like absolute ****. After driving for maybe a half hour or so, it'll bog down real bad and act like it doesnt have any compression. Pedal to the floor, 5th gear, and only getting up to around 30mph going up hill, and back firing like crazy.

I've taken care of all the codes that initially showed up (which was mainly replacing the whole EGR system, new vacuum lines as well, and the ECT)

Ive also rebuilt the whole fuel system up to the injectors (so thats in tank pump, filter, in line pump, and the pressure regulator)
I've installed a new cold air intake because the original had a bunch of tears in the line from the grill to the airbox.
new 02 sensors....

Now im drawing a total blank, and its very strange because in the winter it runs almost perfectly, but as soon as the weather warms up it just becomes a nightmare. It doesnt overheat at all, oil and coolant look totally fine. Any ideas where to look next?

 

have you checked the codes? how many miles?

 

As I mentioned, every code was addressed already. As for mileage, its uncertain. There's only five digits on the odometer .

 

something to think about, i think those years had bad capacitors in the ECU. i had to replace mine in a 94 ranger.

 

What I’d check first (practical order)

Start simple and cheap:

1. Ignition coil
   • Easy swap, relatively inexpensive
   • Very common failure when hot
2. TFI ignition module
   • BIG suspect on late-80s Fords
   • Heat soak failure is textbook
3. Fuel filter
   • Cheap and often overlooked
4. Check spark when it’s acting up
   • If spark is weak or inconsistent → ignition issue confirmed
5. If still unresolved:
   • Fuel pressure test when hot
   • Inspect distributor pickup (PIP)

One quick test you can try

Next time it starts acting up:

• Pull over safely
• Let it cool for 10–15 minutes
• Restart and see if it runs normal again

👉 If it magically improves → heat-related electrical failure (almost certainly ignition)

Bottom line

This does not sound like compression loss—it feels that way because the engine isn’t firing properly under load.

The strongest suspects are:

• Ignition coil
• TFI module
• Distributor pickup