I have a clicking noise coming from the engine. I also noticed that the engine is not idling correctly. It’s making the noise that a spark plug wire would do when it is arching. I did change the plugs last week, but I need to investigate to see what is happening. It also sounds like the noise the O2 sensor makes when it is not working properly. I guess I’ll need to take it in to get a diagnosis

I also have a 2001 and I'm getting a clicking/tapping noise. But it only makes the noise at start up's when the engine is cold. The noise will go away after about 10 seconds after the engine is started.

I have a 2001 Hoe. It is normal for the engine tapping for a few seconds until oil pressure builds up. I heard everything from valve knocking to piston slap.It just the nature of the beast. I use different oil filters, tried a heavier oil, even tried excorcism, didn't help.Some suggest to change to a heavier oil, I wouldn't recommend it though, Stay within your factory guildlines.

I stopped by the dealer this morning and talked to someone there and they heard the clicking noise. He also suggested that the noise was coming from a spark plug wire/ spark plug that is arching. He told me to put the vehicle in a dark garage and try using a water bottle to lightly spray the wires to see if I can get it to spark. I thinking that might work. I just called a parts place and got a quote for 52.00 for oem delphi 7mm wires. The wires were very hard to take off when I changed the plugs last week so I may have damaged one. I think I will just replace all the wires since my tahoe has 101k. I'll follow-up if this was it.... Thanks for all the other suggestions.

The new spark plug wires fixed my problem. I guess when I was replacing my plugs 2 weeks ago I was not careful enough when removing the wires.