engine revs high at startup

I don't know whether it's just my imagination, but I don't remember my engine doing this before... When I start the car in the morning, or after work when it's been sitting for a while, I get a sort of a knock or hesitation before the engine fully comes to life. It's very small but my car has always started very smoothly before. Also, the engine is idling at around 1000 rpm until it warms up. Again, I don't think it's ever done that before.

My car is a 2000 GMC Jimmy 4x4 4dr 4.3L Vortec V6. I recently had the fuel filter replaced along with an oil change, and put in a cold air intake.

I didn't notice any of this until after the fuel filter and oil change, but I had a lot of personal stuff making me crazy so it's possible it was there before.

Any ideas or suggestions?

I don't know whether it's just my imagination, but I don't remember my engine doing this before... When I start the car in the morning, or after work when it's been sitting for a while, I get a sort of a knock or hesitation before the engine fully comes to life. It's very small but my car has always started very smoothly before. Also, the engine is idling at around 1000 rpm until it warms up. Again, I don't think it's ever done that before.

My car is a 2000 GMC Jimmy 4x4 4dr 4.3L Vortec V6. I recently had the fuel filter replaced along with an oil change, and put in a cold air intake.

I didn't notice any of this until after the fuel filter and oil change, but I had a lot of personal stuff making me crazy so it's possible it was there before.

Any ideas or suggestions?

IAC valve could need cleaning.