Random Click sound from engine

Took the truck into Toyota today for 90k service. When I went to pick up the truck, and started it to drive away. Immediately I heard a louder "click click click click" sound coming from the engine. And it was random, it would go on a clicking segment, and then stop, then it would start clicking again.

It's not the normal GRFE clicking noise I'm speaking of. It was a slightly louder, random clicking noise. I've had the truck for 11 years, I've been the only owner, and never has the truck made this noise before.

Fortunately I heard the sound as soon as I turned it on, and had the sales rep come over and confirm he heard it too, and refused to take the truck home until they resolve whatever they did to it.

Hopefully they'll be able to figure out what the deal is. But I was wondering if anyone else has come across this? I'm pretty certain they'll call tomorrow and say they have no idea what the sound is from, and that the engine is fine. I'd like to prepare for such a call and tell them to check so and so before they try to hand it back over to me.

 

My truck always sounds a bit louder after an oil change. The fresh oil tends to make the taco tick a bit more pronounced.

 

This is a sound on top of the taco tick. There's been many oil changes, and like I said it's never made this random tick noise before.