its about 28-48 degrees here in iowa now, when i bouhgt the truck it was in the 60's. now that its colder out my truck makes a funny noise. it sounds like air is purging. it feels like a loss in power. and just like a hissing noise. it goes away if i give it more gas. but i cant figure it out.

 

Its your EBPV (Exhaust Back Pressure Valve). When cold it closes to help build backpressure and heat, warming the motor quicker.

100% normal.

 

thanks, it just sound weird.

 

I've been looking for that noise for 5 years. Why does it seem worse now? Are there parts to replace to quiet it down in cold weather?

 

i talked to a local shop, they said they usually take it out, it has some purpose but, they said not enough to make a difference when removed, more questions about it though, dose it hurt your gas milage?, and is it supost to sound like a purge?

 

when it's making the grinding noise there seems to be a loss of power. Add a little more pedal, it's gone. It's between 1250-1500 RPM's. I've replaced belt tensioners, a pulley and my final thing was I had the transmission torn apart to find the torqe convertor was about shot that added to my noise hunt. Oh, I was also told it was the fan clutch. That was replaced to! I'm about ready to open it up myself as it seems I havent found the right mechanic.