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Low boost, any ideas?

Reverant GTP

Reverant GTP

New member
I have a 2004 Comp G that recently developed a problem of not getting full boost. This is all based off the factory guage and it wont reach full blocks until about 5k. I tried unplugging the bottom vac line off the boost actuator and still nothing. I sprayed brake cleaner around trying to find a vacuum leak but the idle didnt raise at all. The boost actuator arm drops down the full length when the gas is floored as it should. Any ideas?
I do have coolant that is disappearing so i'm pretty sure i need lower intake gaskets. Perhaps under the manifold it is sucking in air which may be causing my issue? I am not sure at this point because on my last few cars when this happened i just unplugged the vac line from the bca then got a new one to solve it. Any ideas and help is appreciated, thanks!
 


The actuator closes fine... If it helps someone my ltft at 65 with cruise control on are -19.5 and will fluctuate to -16.5 sometimes.... my stft fluctuate back n forth between 0 and 3... i do get a couple degrees of kr going up a hill while cruising like this.
 
at wot i get a constant 3-4 degrees of kr.. spike up to 6... ltft stay about -12.5.... 02 b1 950-970... about 12.5 degrees of advance at 4 degrees kr... 140 climbing to 160 kPa... stft stay at 0... I am by fat a novice at tuning and am still learning but i'm sure maybe someone could make and understanding... I have an air intake and the resonator delete right. Not modding further till i get everything in check.
 
Those trims are way out of wack. I would start by checking for a vacuum leak on your lines and gasket surfaces.
 


I already sprayed brake cleaner everywhere so I'm going to guess it may be internal leak from the lower intake? I'm going to scan at idle n see what it says. I read somewhere a vac leak will peg my ltft to 16.4. Also read something about evap can cause a leak if its open or something like that. I'll have to look for more info on that.
 
I've tried different carb cleaners before and it never picked up a vac leak for me... when i was younger they worked but about five years or ive tried a few different brands n they didnt work so i found brake clean works everytime and its only two dollars lol
 
The thing that gets me is I still reach full boost at high rpm... it builds like ID guess a centrifugal would. From a dig when i punch it ill get abouy half then it slowly increases. In first gear it will hit all but the last bar and second gear it will hit full boost about 5k rpms.
 
Just thought i'd give a little update on this. I have an air intake with the cone right on the maf tube just like everyone else. Well i decided to put the maf tube on the throttle body and have a stretch of tube before the maf. What a difference it made! I now get all but the last bar on my factory boost guage. So still searching that issue but decided i'm gonna wait until i change intake gaskets since they are leaking. I also dont get a constant 3-4 degrees of kr. Its erratic but out of ten pulls 7 were 1-2 degrees and the others were 2-3. I still get a very occasional 4 and spike 6 however on one. My o2 b1 is lower also which is around 890-930 depending on the pull. Still running negative fuel trims however and for some reason 100% injector duty on shifts however it is better than previous intake setup where it was 106% on shifts. I'm not sure if that injector duty cycle is normal on a stock car with just an intake?
 


Reverant GTP said:
Just thought i'd give a little update on this. I have an air intake with the cone right on the maf tube just like everyone else. Well i decided to put the maf tube on the throttle body and have a stretch of tube before the maf. What a difference it made! I now get all but the last bar on my factory boost guage. So still searching that issue but decided i'm gonna wait until i change intake gaskets since they are leaking. I also dont get a constant 3-4 degrees of kr. Its erratic but out of ten pulls 7 were 1-2 degrees and the others were 2-3. I still get a very occasional 4 and spike 6 however on one. My o2 b1 is lower also which is around 890-930 depending on the pull. Still running negative fuel trims however and for some reason 100% injector duty on shifts however it is better than previous intake setup where it was 106% on shifts. I'm not sure if that injector duty cycle is normal on a stock car with just an intake?
Click to expand...

U lost me. What do u mean stretch tube?
 
893039_10151495740707432_2002121178_o.jpg
 
I swapped the maf tube and the 22 degree tube around. My guess is the filter right off the end of the maf doesnt allow proper readings. There is no honeycomb to straighten the airflow out so i would guess it needs a run of tubing before it hits the maf. Even the factory air box has a run of a few inches of tube inside before it his maf and i'm gonna guess 2004+ need this to get proper maf readings? Just guessing here but i do know it made a huge difference in my case.
 
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