Help with a strange noise....

[jejjackson]

Now that the weather is getting colder I have noticed a strange sound up to about 1/4 throttle untill the truck warms up. It is like a hissst sound that repeats every second or so while the I'm just barley on the gas. You can even feel it a little at times. What is up? any ideas?

99 F 350 SRW 4x4 crew 7.3 psd bd x monitor, Superchips TDI Gold, Tymar, 36' swampers

[samiam]

I dunno the answer, but I heard a similar funny sound from my early 99 this morning, and it was about 40 degrees outside. once fully warmed up, no funny sound. I have a brand spanking new auto tranny and torque converter, but it seemed like it was coming from near under my feet or maybe near the area of the turbo....

[CUMMINS_KILLA99]

i believe thats your exhaust back pressure valve working you both said it made the noise when it was cold and when the truck warmed up it stopped

[jejjackson]

exhaust back pressure, that sounds about right it would build up and release. Why does this happen? maybe Cat/Muffler stopping up needing to warm up to release the gases enough?????? What do you all think?

[djsdiesel]

the exhaust back pressure will operate when it is cold outside and has met other parameters. This is normal. If you don't like it unplug it. It is there to aid in warmup. I gutted mine and don't notice any real difference in warm up time. On a 99 and up you unplug it on the turbo pedistal just below the centersection of the turbo on a 97 and earlier it is just below the where the intake tube clamps on to the turbo. It will set a code but it will not turn on the CEL unless it is a california emissions model

[vitalidle]

The exhaust back pressure valve is there for engine warmup or to aid it. The valve closes to put a load on the engine. It should open when you hit the gas pedal, or after the truck has warmed up it stays open. Yours might be sticking some. I had the same problem and just unplugged the the electrical connection until I could gut the whole valve.

[vitalidle]

Beat me too it! lol

[jejjackson]

Thanks guys

[sevenmalards]

Mine shuts off when I hit the brake pedal.
It sounds like a jet engine in the early morning with no muffler or cat so I go out and hit the brake to turn it off. I leave really early in the A.M. and TRY not to wake the neighbors.

[turbolariat]

where exactly is this exhaust valve and do i need to worry about it if im doing an exhaust.