Stabler at high speeds

If the check engine is on I belive most likely to be a bad sensor, you can take it to any auto zone and they will read the codes for free, it might be the oxigen sensor or the crankshaft sensor that's giving you problems.

Theyre not expensive and go bad much too often.

Pls rate, thank you

You don't say what year it is, but some have an ignition module with two or more sections for different rpm ranges. The later models may have variable cam timing and if this fails in high rpm mode it will cause this too.

You can bot you shouldn't. I understand it's not good to have car well balanced and stable braking.
If you decide, don't run at high speed.

Suggest you to vehicle charging circuit for a thorough examination.
The first is to measure the battery tester, suggest you use high frequency discharge gauge or battery measurement, the load current is less than 110 of the cases, the minimum voltage shall not be less than 9.6 volts, and remained stable in 5 seconds. If the voltage below 9.6 volts, but can keep stable inside said in 5, excessive discharge, should be timely supplementary charge; if the voltage below 9.6 volts, to maintain stable and rapid decline to 0 volts or close to 0 volts in 5 seconds can not, indicates that the battery failure.
Then check the generator power output, recommend looking for car condition with a multimeter in parallel with the positive and negative poles battery, the output voltage and stepped on the gas check generator in high speed condition is in the 14V positive and negative 0.25V or so, if the lower or higher than the standards, then the generator failure. Use obd2 tools for automotive diagnostics , you can improve vehicle safety performance and driving more safer.

All the Parameter Identifications are preset and you cannot alter them. Though you can achieve stable rpm with or without load by the process which is known as engine tune up, throttle body cleaning and relearning the idle speed control valve.

first check for a vacuum leak.....

it is an SUV, meaning it is top heavy compared with lower slung vehicles, if you are driving at high speed you are asking for a tip and roll and roll. please do this type of driving all by yourself, and limit the number of fatalities. google and read the sorry stories about the early Ford explorer II. I would however, also get a good 4 wheel alignment done and replace the all worn suspension components on this 11 year old vehicle.

sounds like your vehicle speed sensor is broken. here is a tutorial from autozone.com

OPERATION


The vehicle speed sensor is made up of a coil mounted on the transmission and a tooth rotor mounted to the output shaft of the transmission. As each tooth nears the coil, the coil produces an AC voltage pulse. As the vehicle speed increases the number of voltage pulses per second increases.

TESTING


See Figure 1

1. To test the VSS, backprobe the VSS terminals with a high impedance voltmeter (set at the AC voltage scale).
2. Safely raise and support the entire vehicle using jackstands. Make absolutely sure the vehicle is stable.
3. Start the vehicle and place it in gear.
4. Verify that the VSS voltage increases as the drive shaft speed increases.
5. If the VSS voltage is not as specified the VSS may be faulty.

Fig. Fig. 1: Vehicle Speed Sensor (VSS) and vehicle speed signal buffer wiring diagram

REMOVAL & INSTALLATION


See Figure 2

1. Disconnect the negative battery cable.
2. Disengage the electrical connection.
3. Unfasten the sensor retainers.
4. Remove the sensor and gasket or O-ring.

To install:

1. Install the sensor with a new gasket or O-ring.
2. Fasten the sensor retainers.
3. Engage the electrical connections.
4. Connect the negative battery cable.

Fig. Fig. 2: Vehicle Speed Sensor (VSS) location

Your car is not getting hot enough for both fans to operate. One fan and your cooling system is doing the trick.

check for a vaccum leak or test throttle position sensor