Check your wastegate is not stuck and it moves around

also make sure your vac lines on the mbc are in the correct location.

Maybe debris got inside the mbc?

Wastegate arm moves freely, and I have the mbc hooked up correctly.
The nipple in line with the adjusting knob goes to the compressor housing and the nipple adjacent to the main body goes to the wastegate.

is it cutting out or breaking up or is It just holding 9 psi?

No cutting out or breaking up, just a steady flow to 9psi and it holds there (roughly between 8-9psi)

Is the mbc or anything else new or recently put on before the problem started

No this has been on for a while.

Well it could be the turbo is bad the wastegate or the flapper in the exhausts side of the turbo how about with the mbc off is the boost the same 8-9 psi

I was having the same problem. Hallman MBC and I thought it was broken after checking wastegate and debris and found no issues. I was also stuck at 9lbs steady, but I didn't know how much adjustment it needed so I went from there. Started slow and turned it in and no change still at 9lbs. I turned the screw in Pretty far for only 14lbs.


Possibility of your problem also? I was just about to replace my MBC.

Here's two quick ways to test the MBC:

For a really quick and dirty test, disconnect the MBC from the pressure source and wastegate actuator. You will now have two lines connected at one end to your MBC. Then make sure that the screw is turned in pretty far and blow into the pressure source line. If you CAN blow through the MBC with the screw turned in, it's broken. If you CAN'T blow through it, it might still be broken .

For a more definitive test, pull the one line off of the wastegate actuator nipple. You should now have a MBC with the pressure line completely hooked up and the wastegate line disconnected at one end. Next, rubber band a balloon over the open end of the line that normally goes to the wastegate actuator. Again, make sure that the screw on the MBC is turned in good and far. Now pressurize your IC piping to your desired boost (just like you were doing a boost leak test). If the balloon starts to fill up, it means that your MBC isn't doing it's job. If this is the case, turn the screw in more to see if it stops allowing air into the balloon. If you end up turning the screw in all the way, and it still doesn't help, then you know for sure that your MBC is broken.

Note: most MBCs have a small hole in them that allows a small amount of air to escape for legitimate reasons. This is normal.

Ok, I'll try the tests tonight when I get home.

I wasn't turning the knob far enough down. It was kind of stuck at the full open position, but I tightened it more and it started making the spring compressed. Big duh moment. Now im running at 13psi

That's good

At least it was that and you didn't have to spend more money just time

ohlegend said:

I wasn't turning the knob far enough down. It was kind of stuck at the full open position, but I tightened it more and it started making the spring compressed. Big duh moment. Now im running at 13psi

Click to expand...

Thought that was your problem! Glad it's resolved, keep boosting!