Loud hissing noise from exhaust while driving

[CPD4thD]

While cruzing down the road under light acceleration I hear a LOUD hissing noise coming from the exhaust. If I give it some heavy throttle is makes this suctioning noise and goes away. Once I let off the throttle it comes back again. Any ideas as to what this could be? It just started to do it the other day.

[partsguy84823]

Was the truck fully warmed up when you noticed this?

Has it been cooler their lately? (below 35º or so)

My first thought is EBPV, it is a valve that closes after the turbo to increase engine load and decrease warm up time. It is normal for it to cycle under low engine load until the EOT gets to a certain point. (I think 160º, but don't quote me.)

[olblue97]

it's the ebpv i had the same scare 1 week ago it closes to help warm up faster only happens to me whne its below 32 degrees

[troykimber]

that would be the ebpv - exhaust backpressure valve. it's controlled by the pcm and is used to simmulate a load on the motor when it's cold, and helps warm the beast up a little quicker so u can defrost the windshield and warm the cab up. they can also be converted to an exhaust brake for about $15 and some of u're time.

[CPD4thD]

Originally Posted by partsguy84823

Was the truck fully warmed up when you noticed this?

Has it been cooler their lately? (below 35º or so)

My first thought is EBPV, it is a valve that closes after the turbo to increase engine load and decrease warm up time. It is normal for it to cycle under low engine load until the EOT gets to a certain point. (I think 160º, but don't quote me.)

Yep the truck was fully warmed up. It has been in the low 30's high 20's here the past few days. It did it yesterday but then stopped. But its doing it again today. I can hear a dorwning noise from under the hood when it's doing it. It never did this when it was warm out, just started doing it since it's been pretty cold.

[dieseldan2005]

If it is coming on too often, clean the sensor and the ebp tube that goes from the pass side exh manifold. The sensor is located right above the water pump.

[troykimber]

funny - by the time i was done typing there were more posts answering that 4 u.

[CPD4thD]

I don't see this sensor above the water pump, unless im overlooking it or something?

[dieseldan2005]

CODE: PO475 Exhaust Pressure Control Sensor?

Scroll down and the one pic shows the sensor behind the belt pulley. Maybe its not in that location on an OBS.

[CPD4thD]

Originally Posted by dieseldan2005

CODE: PO475 Exhaust Pressure Control Sensor?

Scroll down and the one pic shows the sensor behind the belt pulley. Maybe its not in that location on an OBS.

Found it, I pulled it off and it was packed with black soot like stuff. Cleaned it out with some carb cleaner and sprayed some down into the tube. It seems to be fine now. Thank's alot guys!!