60,000 miles on the truck running level 4 on the EZ all the time.

Sorry if this gets long winded.....

For the past couple of months it has seems that the truck take longer then normal to build boost and not getting as much boost. Also seems like you can hear alot of air air rushing out from under the truck that it didn't use to do, but you can start hearing things when you are looking for a problem. Also at low boost it would blow a pretty good amount of black smoke that it never use to.

Well this weekend I finaly got to hook on a pull something to really check it out, it was about 16,000#. It was pretty obvious right away that the power was not their that use to be, plus the EGT's were running 200-300 degrees higher then they use to. It took longer to get to speed and didn't have the hill pulling power. The most boost it would make was about 25psi, before with a load like that I could get into the 32-34 area pretty easy.

Now on the way back with this load all the suudden like someone through a switch their was a real high pitch whisle, like you would get when you pinch the end of a ballon off and make it whissle. The more boost their was the louder it was, still made the same 25 psi. It did this for about 4 hills and then the noise was gone. About 1 hour latter is came back again, louder and starting at a lower boost and it wasn't going away. It would start right at 9.5 psi of boost and the more you pushed it the louder it got. So I backed it way down and treid to keep the boost down and kept rolling for home. About 60 miles from home it 1/2 fixed its self and the pitch of the whisle changed and I could run it up to 14 psi before it started.

My first though was one of the rubber turbo hoses, but they all look good. And I never lost any boost pressure, other then the fact I was down to 25 to start with. I also though at first maybe the EZ was messed up, but how would that make it whisle?

Any ideas out their? You miss the power once you have had it.

 

Not sure on yours... But my old 91, that sounded familiar. It turned out that the intake bols had loosened up some and the noise was the boost pushing past the gasket. Was really weird and really hard to find. I drove it for a couple months trying to figure out wher this noise was coming from, especially under hard accel, or load. Turns out just tightening up all the intake bolts cured the problem. Mine had like this plate as part of the intake. So it was like an open intake, with a cover on it the the TB sat on. Hope this helps some.

 

maybe look at the intake, before the turbo, thats the only thing i can think of if you looked and ALL the rubber hoses,

or set the idle fast, have somebody hold it at 2000rpm and spray soapy water all over those hoses. on my 97 12 valve a rubber fitting went, couldn't see it at idle obviously, but if i moved the throttle back and forth by hand you could here it let loose. or try it without the EZ

you might have better luck if this was on the high perf forum to

 

I'd say blown turbo hose or loose band clamp.