Can not Bulid Boost while Braking!!!!

[klever]

Recently bought my 87 GN but it does not build boost while braking also the highest boost level I see are 10-11 on my boost guage, also while at idle i step on the gas and dont see any boost change on my boost guage stay nearly at -10 Vaccum, I spray water all over the vaccum lines to check for any leaks and nothing, also check the piping and still nothing, I am new to TR any help will be great. Do i need to change a sensor or something ANY HELP, thanks
87 GN, TA49, 60 lbs Inj, 91 Chip, fuel pump w/Hotwire

 

[BADazzBUICK]

You need to get a scan tool hooked up ASAP. If everything checks out,u might have to turn the boost up.The guy before you might of had it turned down so you wouldnt blow it up.

 

[Boost231]

very true u need a scan tool. if the turbo is a 49 it should spool with a stock converter. if its a bigger turbo then the 49 and a none actory d5 that might be a problem as well

 

[klever]

ok my mechanic has a scan tool.. how do i turn up the boost level?
thanks

 

[Boost231]

via the adjustable wastegate. what kind of scan tool does you mechanic have?

 

[klever]

ok i adj wastegate i wll try that i did research and look lke the shorter the rod the more boost... hope mines is adjustable... my mechanic has a full line of mac tools and snap on but i am reading on this forum and i might be getting a scanmaster to better tune my car...
so the problem why i can not build boost while braking is that my boost levels are too low correct?

 

[BADazzBUICK]

ok i adj wastegate i wll try that i did research and look lke the shorter the rod the more boost... hope mines is adjustable... my mechanic has a full line of mac tools and snap on but i am reading on this forum and i might be getting a scanmaster to better tune my car...
so the problem why i can not build boost while braking is that my boost levels are too low correct?

A BIG maybe.Its prolly a cracked driver header or something like that,but a scan tool will let you know whats going on.DO NOT up the boost till you get scan tool. Id DEF go with scan master(min) as a scan tool.If you have a laptop, direct scan or even a power logger would be better.How long ago did you get the car?

 

[klever]

ok i will try to get the scanmaster or maybe find a friend the has one maybe he can let me borrow it for a week or so.. i just bought the car a month ago and i am truely happy with it just want it to be at his full potential.... i am reading on the forum that in order so for vaccum to be good it must be at -10 up to -30... my boost/vaccum shows -20 at idle so i assume that is okay but if i have a crack leaking manifold how can i tell once i get the scanmaster? also i found a guy locally selling me a pats 2800 stall lock up converter for 150 but said that its new but 6-9 years old dont know if i should buy it....

 

[BADazzBUICK]

The scan master will show if your running rich or lean and when you post your numbers,people on here will be able to figure out what is going on.The reason I say cracked driverside header is because ALL of them crack after a while,yours might not be,how many miles you got on your car?We could guess all day,till you get your scan master we wont know Theres ALOT of help on here. P.S. List ALL your mods. People on here will get you going in the right direction!!

 

[GNVYUS 1]

The car probably has the stock boost solenoid on the passenger side valve cover. Make sure it has the hose on the correct way ( search for photo ) and that there aren't any holes in it.

10-11 psi sounds like you are running off the wastegate alone. After you get the Scanmaster and get the tune down I'd ditch the wastegate solenoid and get a manual boost controller and set it to whatever psi you want.

 

[klever]

ok i got a loaner scanmaster,
87 GN, all stock, 60lbs injectors, TT 91 chip, 340 pump w/hotwire, TA-49.
Vaccum is -20 at idle, while building brake boost I only see 0.5-1 of boost.

Idle
AF = 04
L8 = 29-30
BAT = 13.5-13.6
INT = 128
BL = 134-135
MPH = 00
CLT = 182-184
ATS = 132-140
RPM = 775
TPS = .46
IAC = 21-22
MAL = 00
CC = 245
O2 =699-728

WOT O2 = 816-828, 0.0 = retard

thanks!!

 

[GNVYUS 1]

With the IAC in the low 20's you probably just need to add at least 1psi of base fuel pressure to get the BLM down to 128, don't think there's a vacuum leak. Then since you are fat up top you'll need to pull a bit of fuel in the chip for all gears.

Try reading BLM while brake torquing for us, but the tune might not be the culprit.

 

[BADazzBUICK]

ok i got a loaner scanmaster,
87 GN, all stock, 60lbs injectors, TT 91 chip, 340 pump w/hotwire, TA-49.
Vaccum is -20 at idle, while building brake boost I only see 0.5-1 of boost.

Idle
AF = 04
L8 = 29-30
BAT = 13.5-13.6
INT = 128
BL = 134-135
MPH = 00
CLT = 182-184
ATS = 132-140
RPM = 775
TPS = .46
IAC = 21-22
MAL = 00
CC = 245
O2 =699-728

WOT O2 = 816-828, 0.0 = retard

thanks!!

Your numbers look OK.Your O2's are good to add some boost,I would add a pound at a time,your wastegate should have a nut on it,loosen it up and turn that thing that connects to the puck(dont know what its called) 1 full turn (shorter) equals 1 pound of boost.KEEP 1 eye on the knock and the other on the road till 02's are around 780ish=0 knock.But thats not your problem.when you brake torque it, do the wheels spin at 1# of boost? OR the car just sits there and doesnt build anymore boost?

 

[klever]

ok thanks I will try to up the boost, no tire spin just sits there and does not build any boost, once I let go the brake it gets going it starts to build boost...

Thanks for the help guys

 

[klever]

wow I can not play with my toy, I have a overseas business trip, thanks guys will post again once I come back...