The stopping distance d of a car after the brakes are applied varies directly as the square of the speed r. If a car traveling 40 mph car stop in 90ft, how many feet will it take the same car to stop when it is traveling 90 mph.

Do you know how it works ? What controls it ?

Did you hook up a scan tool an check for DTC'S - diagnostic trouble codes ?

Cruise Control Description and Operation
Cruise control is a speed control system that maintains a desired vehicle speed under normal driving conditions. However, steep grades may cause variations in the selected speeds. The electronic cruise control system has the capability to CRUISE, COAST, RESUME SPEED, ACCELERATE, TAP-UP or TAP-DOWN.
The main parts of the cruise control system are:
• The powertrain control module (PCM)
• The function control switches
• The stop lamp switch assembly
The cruise control system uses the powertrain control module (PCM) to maintain the desired vehicle cruise speed . The PCM assembly contains a low speed limit which will prevent system engagement below a minimum speed of 40 km/h (25 mph). The PCM assembly is not serviceable.
Cruise control operation is controlled through the function control switches located on the multifunction turn signal lever. The cruise control function control switches includes the ON/OFF, SET/COAST, R/A (resume/accelerate). The switch assembly provides driver control of the cruise control system.
The stop lamp switch is used to disengage the cruise control. A cruise control release switch circuit and a stop lamp switch circuit are used. The stop lamp switch is mounted to the brake pedal bracket . To disengage the system the driver presses the brake pedal. The speed of the vehicle at brake actuation will be stored in the memory of the PCM.
With cruise control, the vehicle can maintain a speed of about 40 km/h (25 mph) or more without keeping your foot on the accelerator. When the driver turns off the cruise control ON/OFF switch or ignition switch, the cruise control turns off. The vehicle speed stored in the memory of the PCM will be lost.
Ignition positive voltage is supplied from the HVAC fuse, to the cruise control switch. When the cruise control ON/OFF switch is on, ignition positive voltage is applied to the cruise on switch signal circuit terminal of the PCM. If the driver has not pressed the brake pedal, ignition positive voltage is supplied through the stop lamp switch, TCC/Brake signal contacts to the cruise control brake pedal switch signal circuit terminals of the PCM. Cruise control is canceled when the driver presses the brake pedal. The stop lamp switch contacts close, applying battery positive voltage to the stop lamp signal circuit of the PCM. At the same time, the TCC/Brake contacts of the stop lamp switch open and voltage is removed from the brake pedal signal circuit at the PCM. When pressing the SET/COAST button on the multifunction turn signal lever, ignition positive voltage is applied to the set/coast switch signal terminal of the PCM. When pressing the R/A (resume/accelerate) on the control switch, ignition positive voltage is applied to the resume/accelerate switch signal terminal of the PCM.
When the cruise switch is in the ON position, and the driver presses the SET/COAST button, the PCM then checks to see that the cruise control enable criteria is met. If the cruise control criteria has been met the PCM sends a class 2 message to the instrument panel cluster (IPC) to illuminate the cruise light.
The PCM will inhibit cruise control:
• When the PCM detects that the center high mounted stop lamp (CHMSL) in not operating properly.
• When vehicle speed is less than 40 km/h (25 mph).
• When in PARK, REVERSE, NEUTRAL, or 1st gear.
• With low engine RPM
• With high engine RPM (fuel cut-off)
• When vehicle speed is to high
• When an over or under charged battery voltage condition exists
• Antilock brake system/traction control system is active for more than 2 seconds
If the PCM determines that any of the cruise control inhibit conditions are present, the PCM will disengage the cruise control. If the PCM disables the cruise control for an inhibiting event it will record the reason for disengagement in the Disengage Definition data file.

Do you know how to test electrical circuits with a DVOM - digital volt ohmmeter, looking at a wiring diagram for the CC so you know what wires to test , if not your best bet might be to take it to a qualified repair shop .

`right one of two problems ,firstly remove the rear drums and check for a fluid leak as a slight smear of fluid will cause the exact problems you describe ,if the rear shoes are dry then push the cylinder each side to make sure its not seized ,secondly check the load sensing valve which will be under the chassis above the back axle,if that appears ok and not seized then remove the master cylinder and take the piston out and check the rubbers and the cylinder bore for wear ,but mainly this fault is caused by the brake shoes having a slight amount of brake fluid contamination and it causes the brakes to grab

it is not how many miles but the type of driving.

here is a OBD2 drive cycle test.

Generic OBD II "Drive Cycle" Most OBD II ("On-Board Diagnostics II") diagnostic monitors will run at some time during normal operation of the vehicle.
However, to satisy all of the different Trip enable criteria and run all of the OBD II diagnostic monitors, the vehicle must be driven under a variety of conditions. The following drive cycle will (theoretically) allow all monitors to run on (??) vehicle. (Note: Drive cycle specifics vary by vehicle!)

1. Ensure that the fuel tank is between 1/4 and 3/4 full.
2. Start cold (below 86°F /30°C) and warm up until engine coolant temperature is at least 160° F (typically requires at least one minute; up to 3 minutes).
3. Accelerate to 40-55 MPH at 25% throttle and maintain speed for five minutes.
4. Decelerate without using the brake (coast down) to 20 MPH or less, then stop the vehicle. Allow the engine to idle for 10 seconds, turn the key off, and wait one minute.
5. Restart and accelerate to 40-55 MPH at 25% throttle and maintain speed for two minutes.
6. Decelerate with using the brake [or the clutch!] by coasting down to 20 MPH or less, then stop the vehicle. Allow the engine to idle for 10 seconds, turn the key off, and wait one minute.

A complete check-up of the car which should include but not be limited to:

1. Change the oil (when was the last time you changed it?) Change the oil filter & the air filter (again, when were they changed last?)
2. Check the coolant and brake fluid
3. Check the brake pads - inspect all lights including turning signals (for safetys sake)
4. Check the air pressure in the tires (including your spare tire) Check your car's alignment, this can cause uneven wear on your tires and it will believe it or not contribute to making the trip more exhausting.

Make sure you get a good rest the night/day before you depart. - if you begin to doze off dont hesitate to stop at a rest stop. Dont fight against your body, if you are tired, stop and take a 30 minute power nap, wash your face and drink a cup of coffee before you get back on the road.
Make sure you have a bottle of water in the car and plenty of good music to listen to. - Speed wise I suggest you dont travel at more than 10mph over the speed limit, traveling a little over (up to 10 mph) is tolerated by police, but I strongly sugest going 5 mph over the limit, set the cruise control and enjoy the trip without worrying about potential fines. If you do the math, the difference in time traveled is not so great:
speed limit = 70 mph (just as an example) 1300 miles @ 70 mph = 18 hours 36 minutes 1300 miles @ 75 mph = 17 hours and 20 minutes 1300 miles @ 80 mph = 16 hours 15 minutes the difference between traveling 75 or 80 is only 1 hours and 5 minutes. Not worth risking a fine for