Clicking noise from engine

[computerdna]

Dear all,

I have a 01 QX4 with 100k miles. Since 3 months ago, I have noticed a clicking noise from the engine. It only has noise when the car is warm and only happens for the first five minutes and during acceleration.

Everything is fine in the morning with a cold start. After the car completely warms up (driving for 20 minutes), then stop the car for 10 minutes, and start car and drive again then clicking noise will appear. More noticeable during up hill and around 2k RPM during acceleration for the fist 5-10 minutes, then noise disappears.

Another condition the clicking noise appears is that if I stay on a traffic jam (stop and go / bumper to bumper traffic) for 20 mins, the clicking noise appears during acceleration, around 2k RPM.

When the clicking noise appears, RPM higher than 2.5k would make it less noticeable and completely gone after 3k+ RPM. Most noticeable during acceleration at around 1.5k-2.5k RPM. Noise also disappears if I release the gas pedal.

Recently the “Service Engine Soon” light came on with code P0171 – Fuel Trim too lean. I don’t think this has anything to do with the clicking noise, because noise appears 3 month ago and the light just came on.

I am a fan of this forum and have since learnt a lot. Any help would be greatly appreciated.

Thanks in advance.John

[maxnix]

It only has noise when the car is warm and only happens for the first five minutes and during acceleration.

But the first five minutes it is heating to operating temperature from cold.......

[computerdna]

First 5 minutes at warm/hot start - which means the car is warm/hot to begin with. Hope I made it clear.