Belived it or not - Strange sound from engine

This is my second Toyota Truck. First was a '88 Hi-Lux - name before they started using Tacoma. I do wish I still had the '88 sometimes as it was so simple and cheap. Had 264k on it when I sold it and running strong.

I now own a 2007 Tacoma Double Cab 4x4. I live north of Tucson, AZ, in Oro Valley. I use the K&N airfilter so I can clean it rather than buying a new one. Seems to use lots of airfilters in the desert. Last Fall 2008, when it was getting cooler, when I started the truck it rumbled like something was loose under the hood. The noise dissapates when the truck warms up. Warmed up in the spring and the noise was gone at start up.

Now that it is around 60 in the mornings, the noise has returned. Last year I would use the K&N grease around the airfilter but it did not make any difference. I really don't know what is causing the noise but assume it is the K&N airfilter since everything else is OE.

Any suggestions like maybe a loose engine cover?

 

I had a sound that I thought as a lose engine cover and it was a bracket on the intake pipe they put a different bracket on mine and I have not heard it since. It was funny because I took it to the dealer like 3 times for the noise and every time I would get there then noise would stop so I left my truck and they drove it first thing in the morning heard it and found it.

 

It's normal check out this thread : http://www.toyotanation.com/forum/showthread.php?t=285993

 

Thanks. Will check it out.