Engine shutter my engine shutters while maintaining a constant speed like on the hwy. It doesnt do it while accelerating or coasting or idle. Example. if im on a flat hwy no hills or curves at 50 mph the engine will **** and shutter contantly if i let off the gas peddle the shutter stops. if i go up a hill and cause the engine to pull like in accelerating the shutter stops. what could be the issue.

It is HVAC 1fuse #39 in the rear fuse block ,this powers the on/off switch for cruise control ! Fuse Block - Rear Beneath the left rear seat. What engine does it have ? 4.2 L or 5.3 l There is no vacuum involved in the operation of the cruise control ! Your vehicle has electronic throttle control .
Cruise control is a speed control system that maintains a desired vehicle speed under normal driving conditions at vehicle speeds above 40 km/h (25 mph). Steep grades may cause variations in the selected vehicle speeds.
The following are the main components of the Cruise Control System:
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The powertrain control module (PCM)

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The On/Off switch

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The Resume/Accel switch

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The Set/Coast switch

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The TCC brake switch

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The stop lamp switch

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The throttle actuator control (TAC) motor

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The vehicle speed sensor

Cruise Control Engaged
The cruise control system will engage and adjust the vehicle speed based on the activation of the following cruise control switches:
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On/Off

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Resume/Accel.

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Set/Coast

The cruise control switches are located on the multifunction/turn signal lever.
The powertrain control module (PCM) monitors the signal circuits of the cruise control switches in order to determine when to capture and maintain the selected vehicle speed. The PCM uses the throttle actuator control (TAC) module motor in order to control the vehicle speed. For further information on the TAC System, refer to Throttle Actuator Control (TAC) System Description in Engine Controls - 4.2 L.
Ignition positive voltage is supplied from the 10 ampere HVAC 1 fuse to the cruise control switch via the ignition 3 voltage circuit. When the normally open cruise control On/Off switch is turned On, the switch closes and the PCM detects a high signal voltage on the cruise control on switch signal circuit. When the normally open Set/Coast switch is pressed, the switch closes and the PCM detects a high signal voltage on the cruise control set/coast switch signal circuit. To engage the cruise control system, turn the On/Off switch On and momentarily press the Set/Coast switch. The PCM will confirm that the cruise control enable criteria has been achieved. The PCM will engage the cruise control system and record the selected vehicle speed. The PCM sends a class 2 message to the instrument panel cluster in order to illuminate the cruise control indicator. Pressing the accelerator pedal, while the cruise control system is engaged, will allow the driver to override the cruise control system in order to accelerate the vehicle beyond the current set vehicle speed. When the accelerator pedal is released, the vehicle will decelerate and resume the current set vehicle speed. The driver can also override the current set vehicle speed via the Set/Coast switch and the Resume/Accel switch. When the cruise control system is engaged, pressing and holding the Set/Coast switch will allow the vehicle to decelerate from the current set vehicle speed without deactivating the cruise control system. When the Set/Coast switch is released, the PCM will record the vehicle speed and maintain the vehicle speed as the new set vehicle speed. When the cruise control system is engaged, momentarily pressing the Set/Coast switch will allow the vehicle to decelerate at 1.6 km/h (1 mph) increments for each time that the Set/Coast is momentarily pressed, with a minimum vehicle speed of 37 km/h (23 mph). When the normally open Resume/Accel switch is activated, the switch closes and the PCM detects a high signal voltage on the cruise control resume/accel switch signal circuit. Activating and holding the Resume/Accel switch, when the cruise control system is engaged, will allow the vehicle to accelerate to a greater vehicle speed than the current set vehicle speed. When the Resume/Accel switch is released, the PCM will record the vehicle speed and maintain the vehicle speed as the new set vehicle speed. When the cruise control system is engaged, momentarily activating the Resume/Accel switch will allow the vehicle to accelerate at 1.6 km/h (1 mph) increments for each time that the Resume/Accel switch is momentarily activated, with the maximum acceleration total of 16 km/h (10 mph) over the current set vehicle speed . Momentarily activating the Resume/Accel switch, after the cruise control system has been disengaged by pressing the brake pedal, will recall the previous set vehicle speed that is recorded in the PCM.

Throttle positioning sensor.might have a vacuum leak to throttle body

Check your air filter

Problem with electronic throttle control maybe. Any light's lit on the instrument cluster or messages engine power reduced . Could be a sign a position sensor is going bad . The gas pedal assembly has to sensors as does the throttle body . You could try cleaning the throttle body bore . Having a qualified repair shop hook up a diagnostic scan tool to view sensor data would be a good thing .
007 Idle Speed Problems Scan Data for Idle
1 reason your cars throttle body needs cleaning Gain lost horsepower and...

What speed are you going when it chugs?
It could be as simple as a bad spark plug or a spark plug wire/boot grounding out.
When spark plug boots get old, the rubber cracks and lets voltage arc out the side and to the engine instead of through the plug.
This will be most noticeable when trying to maintain a speed of over 40 mph, or under mild acceleration.
The reason for being noticeable at this speed/acceleration level is that the transmission torque converter will be locked, transferring the vibration from any engine miss straight through to the wheels.

sounds like a catalytic converter - runs good but lacks power - the back pressure keeps the engine from being able to accelerate under load - good luck :O)

This can be caused by a faulty throttle position sensor (TPS). It will normally be found on the end of the throttle shaft oposite the cable connection. They are fairly simple to replace, and cost less than $50.

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.

What was the code in the computer?

COULD BE THE ENGINE CONTROL UNIT.
A PROBLEM FOR HONDA.