2002 Silverado diesel click on acceleration

I have a 2002 Silverado with 23,000. This morning when I started driving the truck and reached 30-40 mph it made a loud clicking sound upon acceleration ( coming from the area of the gas pedal ) When I
took my foot off the accelerator the sound stopped. It did this for about 3 minutes and then stopped doing it, and did not do it for the remainder of a 50 mile trip.
I'm heading out of town with this truck on Wed for a 400 mile trip - and an a bit nervous needless to say. Anyone experience this before or have any ideas what may have caused this. Temps today in the 90's - if it could be head related some how.
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You don't mention if this was a single click, a constant clicking or an occasional click every 15-20 seconds or so. Also, how loud was it and did you feel any changes in the motor's smoothness, power delivery, etc. Did you feel the click in the accelerator pedal or was it just a sound only without feeling anything.
First guess is what you are hearing is nothing more than the AC compressor clutch either engaging or disengaging, but that is only a blind guess without more info.
Cheers - Jonathan

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I would be suspicious of the throttle sensor.
Jim

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