We have a 2001 Ford Ranger 3.0L and changed the following:

1. The plugs and wires
2. Coil Pack
3. Fuel Pump
4. Oxygen Sensor
5. Cam Sensor


The truck only has 51000 miles on it and appears to be well maintained except for this issue.

 

Something you can try; unplug the alternator plug and drive the vehicle . If the problem is gone the alt is faulty.
There are other things that can cause those symptoms, but a good scan tool should capture what is happening at those speeds.

 

check the vacum lines and your pcv vaulve.

 

The senario sound like a "DEAD" spot in the TPS which causes the injectors to shut down momentarily. Use a DVM to check the resistance reading on the TPS to verify. Look for a momentary loss of resistant to confirm.