To be honest with you Seth, I disabled mine and just let it warm up before rolling. It became a big PITA with the noise of a jet and the throttle response. I'm colder than you up here and I see no Ill effects.

Denny

 

 

I believe that it's all temp based using your IAT vs EOT but I don't know what the triggering numbers are. Mine went out when the van turbo went in because it had to. So...until your oil temp reaches the necessary temp it will close. Under heavy fuel it should open up. And watch your EGT's while it's closed, they will climb.

 

What year is the truck? The EBPV system should kick in on a cold start with EOT ~32 degrees or lower depending on some other sensors such as IAT. At your low temperatures I'm sure it's actuating though. Depending on the PCM code and year of truck the PCM looks at EOT to determine if operation is necessary. When the truck first starts in cold weather the PCM will cycle the EBPV and expects back pressure from the EBP sensor. If it see's back pressure it assumes a working assembly, if not it disables the function. This operation only occurs if the EOT is below ~135 degrees, depending on the PCM code and year of truck. Anything above ~135 degrees the PCM could care less and assumes engine is warmed enough and disables the function on a restart.

Here's the kicker though. On my 97 the function won't go away until EOT is ~175 degrees or above and if still driving, such as waiting for a light change and it drops below ~175 degrees the function continues If monitoring EOT and I see "say" 150 degrees, kill the engine and restart the function is disabled and never comes on during the rest of the driving cycle. On cold mornings it's hard to get that engine temperature up to that level.

I'm pretty much an expert on the 97 model EBPV system operation but not so much on my 99. You indicated the hissing sound which is probably the valve closing. Demand for more power by the foot should open the valve but this takes a few seconds due to the mechanical nature of the device, hard to do in snow and ice conditions. If you can monitor the EBP sensor data this becomes clear as you will see higher back pressures while driving, as much as 43 PSI. Usually when cruising it's in the upper 20's to mid 30's.

 

Mark, I've never seen EGT's climb as boost is zero with higher EBPV pressure, cruising, if anything they go down. Somehow the PCM compensates fueling, don't have a clue how though. Of course this is stock injectors and PCM programming so anything else I'm sure it would affect what you indicated.

 

Right near my house here there's a hill that I have to climb at a slow pace and when that valve is closed the EGT's hit 1000 quickly (when I had the valve). But then mine is live tuned and the PCM adjusting for that might be taken out of the mix.

 

I would check to see that the EBPV tube is clear.

 

 

In answer to your adjustment question, there is an adjustment procedure that gets the EBPV preload within spec but it is done on the bench with a spring scale. When I replaced my turbo a few years ago I did the adjustment and although I seldom visit cold country, when I do the EBPV operation is great. It raises my idle soon after starting but doesn't seem to affect normal driving except for slightly reduced power, but I don't ever push it hard when it is cold anyway.

 

This is the answer.

If the backpressure valve continues to remain closed when accelerating, the sensor tube is clogged with soot.

 

Another possibility that I rarely see mentioned -- the actual EBPV can get stuck shut. It happened to me and I had no boost and no power. I had to disconnect the actuator rod and spin it with a vise-grip, and pull with considerable force to pull the rod out, and get the flapper open. I believe I used a piece of mechanic wire to tie the rod where it couldn't shut.

Eventually, I'll get a new non-EBPV pedestal but for right now it works. It must not happen very frequently because I never see it mentioned, but it is a possibility.

 

Mark, you are correct, I misspoke, sorry Guess what I was trying to say is the EGT's never went above a critical mark anytime when accelerating with stock components and valve working.

You are correct. It's a bit concerning but if you can monitor EBP sensor when driving it becomes clear what the PCM is trying to do vs throttle response. In winter months it's an interesting parameter to watch along with EOT. Only once did my observations fail over the years as the engine temp (EOT) was up and no operation on the valve. Pulled into a fast food drive in to get breakfast and pulling out the valve closed again but outside temps were about 9 degrees and in freezing fog. Guess AIT has some input on this decision.