warm up valve

When I start my 7.3 in cold weather, a butterfly valve just after the turbo closes to hold exhaust gasses back to help with warming the engine up. After a few minutes, it opens back up. Once I start driving, it keeps closing. No matter how warm the engine is, the valve keeps closing. I have to...

Hello all, I have a 2001 7.3 with 230K miles on it. I rebuilt the backpressure valve assembly a couple years ago, new guts, seals etc and it has been working fine last winter. Now that is getting cool enough to start using it again I have noticed that after it kicks in for a minute or so it...