2002 impala and engine clicking

I have a 2002 Impala with 3.4.  Car has 44K miles.  When I start car engine makes a clicking/tapping noise, which gets faster/louder when I drive.  Problem goes away after about 4 minutes, when engine warm.  Anyone experience this? Possible solutions?  Thanks.

sounds like an exhaust leak

like mentioned. could be exhaust leak. more apparent under acceleration.
But since you say it goes away away after about 4 minutes- could be cold carbon knock. I doubt its the piston slap like the V8's had a few yrs ago in the subs and tahoes.
Cold carbon knock is also seen on the I-6 engines used on the trailblazers and similar SUVs.
A tempory fix on the I-6 is to run a bottle of Chevron techron. this helps get rid of the carbon buildup. It does quiet it down for a few months.
It eventually returns after some time on the I6. Using high quality gas helps avoid this.
If you havent- run a bottle of techron.
How about your oil? is it up to level?

I had the clicking on my Impala too (also a 3.4) but mine was from the sluge build up from the lower intake leaking coolant into the crank case. after I fixed the gasket I used a high detergent diesel engine oil and it cleared all the build up out, I only ran it with that oil for about 1500 miles and it's never had a click again. 130,000 miles and still going (here is a hint... if you have a bunch of gooey stuff, like a tan slime on the inside of your oil fill cap, your lower intake gasket is leaking coolant into your crank case) this worked for me!!

it could be that there is a leak on your chevrolet exhaust system. where the manifold hits the block? Gets tighter when the engine warms? You may also benefit from checking your oil level now and adding a bit to fill.

Sounds like hydraulic lifters tapping until the oil pressure builds up. 

I'm no mechanic, but I bet it's related to the collant mixed into the oil as stated by Twizzle12 (above). I have an 03 Impalla with the 3.4. I heard the clicking one day, and igored it. Then a week later I couldn't get the car to heat. Turns out I need a new intake gasket. Other research points to the mixing of oil and coolant when the gasket leaks. Good luck!