2G vacuum/Boost leak??

[2g99]

ok so when i first start my car, when it is cold or warm, my vacuum will be around 10 and as i let it idle or drive around for about 30 seconds to 1 min. it will go to 16-17.
i have done a smoke test to my intake manifold by unplugging a vacuum hose and feeding the smoke through the hose into the manifold, and i found nothing, no leaks at all?!
also when i let it idle i can hear a slight hissing sound from my intake manifold, it sounds like it is coming from somewhere on the bottom of it?

ok and when i do a pull my boost will hit 14psi the drop to 11psi as soon at it hits the 14psi. and it will hold 11 psi just fine. does this sound like a boost leak or just a normal boost spike??
while i was doing the smoke test on the manifold, i decided to see if it will show any leaks if hooked the smoke machine up to my uicp and let it go all the way through my uicp-intercooler-licp-turbo-intake. once again i didnt get any leaks.
but doesnt it have to be pressurized to show my boost leaks??
i do have a Manual boost controller but its a homemade one the owner before me made. so its a little hard to set it at a consistent PSI

do u guys think i have a vacuum leak or boost leak, or does it sound like i my timing is slightly off.?? if so do u think by fixing my timing it will fix my boost problem to?

any help will be greatly appreciated

thanks guys
-2G99

 

[GsxMan98]

Maybe try doing a boost leak test. But if anything vaccum would be lower after letting it run then increase. Kinda sounds wierd.

 

[jcarmichael]

if you have aftermarket guage not sure this is any help, but I was getting a reading of 7 mg when I am usually around 20mg and found I had cut the line from my hood closing on it. yet again not sure it will help because you said it gets better as you drive it. but mine wasnt reading 7 always it would change so its a possibility

 

[2g99]

it also changes if i just let it idle, its usually around 10mg only for the first minute of start up, and my engine can be cold or warm

 

[1990AWD]

Does it sound like the engine is laboring a little? If it's only on startup, it could be because the engine runs richer at startup and it under load from the alternator.

As far as the boost spiking, it could be as simple as having too long of lines for your MBC.

 

[2g99]

Does it sound like the engine is laboring a little? If it's only on startup, it could be because the engine runs richer at startup and it under load from the alternator.

As far as the boost spiking, it could be as simple as having too long of lines for your MBC.

any way to fix the vacuum at start up? like maybe timing??

an ill try to shorten my lines to my MBC

Thanks

 

[kennygw]

well on your smoke test, are you pressurizing all the way up to atleast 15 pounds? If its only pressurizing up to a couple pounds it's not gonna show a leak.

 

[91awd26]

Making a "boost leak tester" is something easy and very usefull to do. Also does your mbc have a small bleeder hole in the nipple going to the wastegate? We had a similar problem with making boost (15psi) and having it drop off considerably but then hold at 5psi every time and after drilling a small bleeder hole in that nipple it made a solid 15psi and held to redline. Just an idea.

 

[Hugolm10]

If the car runs good n it's just boost that isn't holding then I doubt it's timing do a leak test using soap and water I find it easier and more accurate... U might also want to try another mbc I have a big feeling it will be that since it might not be holding boost

 

[spooling hard]

Not timing. I would do a boost leak/leak down test and look for cracked or torn vacuum lines. If it was a vacuum leak you would have an abnormally high idle and it would feel a lot slower than it should be.