Boost problem in 5th gear only

[I am Technoman]

Rob, check for leaks around the pipes. Also check vacuum lines. Can you boost normal in other gears with no hesitating?

[I am Technoman]

What are you teeing off of on the manifold for vacuum for the BOV? try a new location for the BOV vacuum line.

[I am Technoman]

Humm I would need to look for myself.

[MikeMurphy]

I bet your sucking air in through the BOV...maybe. See the bov closes when the vaccuum is gone, but by closing it adds to the vaccuum, therefor opening itself again. At one point is the BOV set to open? Where is it hooked up to the intake? Just an idea.

Maybe check some trivial stuff like any dirt on your filter, and maybe its location and what high winds effect would have on it if the BOV activation setting was too low.

That is all I can think of, and even that is obviously a stretch. Good luck! =)

edit: on second read i think im dumb. ignore my comment :oface

[fiznat]

I dont see how the transmission gear should have anything to do with how the turbo setup behaves. Correct me if I'm wrong, but to the engine, 3,000 RPM is 3,000 RPM no matter what gear it's in, right? I mean, not like the engine is doing something different depending on gear, its just moving through it's rev range over and over again.

If I'm right about that, then maybe your problem is a matter of speed rather than actual gearing? What happens if you're cruising in 5th gear and then downshift and accelerate? It's fine then? I donno... maybe problems with low boost at high speeds or something.... it just doesnt make sense that the gearing should have anything to do with how the engine behaves

[fiznat]

what happens if you get up to like 60mph, put it in neutral and let the engine rev down, and then rev it slowly while you're in neutral (while still hopefully going ~60mph)? Still the same problems, or does it only happen while you're in gear at that speed?

[I am Technoman]

I would think there would be a lesser load on the motor in 5th gear but in the turbo system should not change but + - What kind of blow off valve do you have and can you borrow another BOV from someone else to test?

[fiznat]

dude calm down, we gotcha. it's just a kinda funky problem.

[MikeMurphy]

isolate the problem! swap your BOV and see if that fixes it, or close it off somehow.

[MikeMurphy]

What I would do. Keep in mind im scraping the bottom of the barrel with these ideas.

rule out the BOV! swap it.if you have another ECU you can try. try that if the BOV isnt it.

best of luck to you! Share your solution with us later!

[kettnerc]

Not sure if you have a jwt ecu or not, but I once noticed that the nissan ecu has a 5th gear trip line.. meaning that when you are in fifth gear and only fifth, the ecu knows. I'm not sure why this is important, but it's not so far fetched to imagine that the ecu has a slightly different fuel map in fifth gear for cruising and perhaps this map wasn't reprogrammed (but the normal map was) and thus when it sees boost, it freaks.

Comments?

[3rD GeAr]

it sounds to me like ur clutch is slipping. maybe? do u have an upgraded clutch?

[MikeMurphy]

so have you done anything to it yet?

[C-Kwik]

Maybe try blocking the signal to the BOV to isolate if that is the problem. Since you tried using a different one, maybe it's not the BOV at all. Take care not to slam the throttle shut unnecessarily while doing this to keep surge to a minimum.