Short grunt sound 30 seconds after starting

2.7 MT. After the idle kicks down, I hear like a short, one time "sprunk" sound coming from engine area. What is that?

 

Bump

 

Mine does it to. I believe its a secondary air pump for the cylinders on startup.

 

Mine too!

 

Same here. It's normal.

 

ABS pump.

 

Thanks fellers. Case closed.

 

Op is yours sometimes pretty loud? And only happen when you start the truck up cold for the first time?

 

Not very loud, just kinda like you stepped on an old squirrel or something. And yes, it seems to be only when it's cold, but I could be wrong on that... I only hear it when I start the truck in the morning to warm it up and start walking away... that's when I hear it. All the other times I start the truck, I stay in it and usually have the tunes going 5 seconds later

 

Same here lol I keep trying to tell myself its normal, but its hard too lol