I have an 88 ranger 4x4 with the 2.9 and 5 speed. When you first start the truck it runs fine. After running for about 1 and a half minutes it will start running really rough. will barely pull out of it's own tracks. If you shut it off and start it right back up it will again run fine for about a minute and a half. Any idea's?
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Could be computer issue, there are some time frames in the computer that are based on Boot up, so turning key off and then back on would reset the computers timers.
Giving the same 90second run time each time so not "heat based" issue.
There are 3 blue capacitors in your computer that can leak after 20 years or so, causing odd issues.
You can see them here:
http://www.auto-diagnostics.info/ford_eec_iv
And its FREE to have a look inside the computer, you could spot corrosion or other issues inside.
Cost about $5 to change all 3 capacitors
If you run it longer does it eventually start to run OK?
If not then I would look at TFI module issue or Coil
Read here for TFI:
https://therangerstation.com/tech_library/TFI_Diagnostic.shtml
Ignition coils are tricky to test because they operate as almost a dead short, almost, and that difference allows them to get good spark but also produce alot of heat.
And that heat can cause them to misfire, even after 90seconds
These would be HEAT related, not time related.
Fuel filter or fuel pump, longer shot, could be either is not providing fuel capacity required, engine is simply running out of gas as demand increases so runs rough
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