2G Brake system vac/boost leak?

[Artago]

I'm pretty sure I have a major boost leak somewhere because under boost I max out my AEM WB on the rich side at only 10-12 psi and the car misfires like a bucking bronco.

I've noticed when I'm sitting at a light in neutral and I step on the brake, the AFR goes lean. Around 16-18 AFR lean. The car then tries to go back to stoichiometry and levels out around 14.9-15.1. While still standing on the brake, if I let go, it goes lean again.

The symptoms are weird. Brake in, goes lean then levels out. Lift, goes lean again.

Do I have a vac leak in the brake system? Can the brake booster leak? Also, my ABS stopped working properly (it would kick in under light braking, making it impossible to brake without it kicking in) so I pulled the fuse.

Thoughts, opinions, advice?

 

[stiggity99]

I did a boost leak test on my Eclipse for the first time, and here, when I put it together I used a straight piece of hose to connect the booster to the intake, not even thinking it will make the booster go under pressure. Plus, I was leaking mad pressure right at the booster, while testing. Quick, I went and found a compatible check valve, installed it in 2mins, and now 25psi takes a good minute to leak down to zero, and I didn't have all my valves shut (I forgot how to perform that procedure). Hope this helps...

 

[1990TSIAWDTALON]

You should have something like this. Mine didn't have a check valve either and I need to replace the booster now. Anyway, this is what I use, you decide where you get it.
Search for this in Ebay:
3/8" (10mm) Inline Check Valve Fuel Diesel Liquid Air One Way Non Return

 

[93AWDDSM]

Wow, so a 3/8” check valve is put in the IM to brake booster line to prevent leaks/prevent early failure of brake booster?

 

[1990TSIAWDTALON]

It prevents the brake booster from seeing "boost" so you don't blow out the diaphram.

 

[Artago]

It prevents the brake booster from seeing "boost" so you don't blow out the diaphram.

How do you know if I've blown it out? Is there a test you can do without removing it from the car?

 

[1990TSIAWDTALON]

Yep, pull a vacuum on it. See if it holds, if not, like mine, then it has a bad diaphram. If you can BLOW thru the line or SUCK thru the line then the diaphram has a leak. I found mine doing a BLT.

 

[Artago]

Yep, pull a vacuum on it. See if it holds, if not, like mine, then it has a bad diaphram. If you can BLOW thru the line or SUCK thru the line then the diaphram has a leak. I found mine doing a BLT.

Disconnect it at the intake manifold and test the line, check valve, and diaphragm all at once?

 

[1990TSIAWDTALON]

Yep, or take out the check valve and just test the booster diaphragm for leaks. It should hold a vacuum. DO NOT PRESSURIZE THE BOOSTER. Just FYI.