How big off a boost leak?

[bcjjones]

My car just recently started bucking under WOT only. My idle is steady as can be, not surge and no high idle at all. Did a boost leak check and could only hear air leaking out of my throttle body shaft seals maybe. When listening to it and moving the shaft by pushing on the spring part (not actually opening and closing the TB) just pushing down on it, the sound of the air changes. So that's why im assuming I have a small leak from the shaft seals. Would be a very tiny leak if any, because its hard to even tell if its leaking.

How big of a boost leak would cause the car to buck under WOT only? Im going to check my plugs and wires tomorrow. Also have a spare TPS im going to just change out the one on it, but im not getting a check engine light.

Found a guy here in town selling a "rebuilt" throttle body locally. Hard to trust anyone so is there anyway to tell if the shaft seals are good on it without taking it apart? I would just replace mine but one of the nuts is stripped out and wont come off.

Sorry to be so long and I appreciate yalls time!

 

[WES_393]

Leaky shaft seals aren't enough to cause serious running conditions. I would suggest getting a bottle of soapy water, pressurizing the entire intake about 5psi more than you plan to run, and then spraying down all the pipes. This is a much more helpful approach than just listening for leaks.

 

[xxNocturnalxx]

Well, how fast does it drop from Xpsi. to 0?

 

[bcjjones]

Yea sorry, to clarify I did and do use soapy water when doing a BLT. Didnt see any air coming from anywhere, including the throttle body. Ill re check again today.

The boost builds slower then normal and doesnt fall all the way to zero. It will build to. 22-23 psi (where I have it set) and will bounce between 19-20 psi and about 23 psi?

 

[montm82]

I would first start off with replacing the throttle body, then running a second leak test and then taking it from there.

 

[bcjjones]

Im assuming it would be pretty hard for air to push past the throttle body seals hard enough to create bubbles in the soapy water?

Also, if I were to by a used/rebuilt TB, is there anyway to check the seals?

 

[curt-s]

You actually need very little air to create a bubble in soapy water. I had the smallest of pinhole leak in an intercooler endcap weld, barely even enough to see, but 20psi shot air out of there quite readily when I did a BLT.

 

[bcjjones]

Yea I understand that, but only thought the shaft seals would be a little harder is because the ait has to make it past the spring and everything on one side and the TPS in the other before it would reach the soap.

 

[Dvcaptainm]

I had a phantom leak on my TB and it ended up being the elbow gasket, the corner of it wasnt sealed and even with the soap water it wasnt truly visible as it was on the bottom

 

[bcjjones]

I was going to replace the TB gaskets after work today also. Thanks for the suggestion. The reason I was thinking that was because maybe when im pressing down on the spring of the TB its actually just creating a bigger gap in the possible blown TB gasket(s)

 

[2wdlaser]

I"ve had the tiniest of holes in one of my ic pipes and it cause my car to do that. I mean I could barley see it.