Hi all.


Had the infamous codes P0171 and P0174. Also occasionally reduced performance message. Fuel trims hovering around 15% on the rich side. Revving to 2500 rpm returned trims to around zero. Suspected air leak.
Spraying with carb cleaner while monitoring fuel trims indicated leak at lower left side of throttle body. Suspected part load breather tube connection to TB.
To get at it you have to remove TB or coolant tank.
Removed TB, hardest part getting the coolant lines off. Almost no coolant spilled out.
Part load breather hose very brittle and totally crushed around T-piece connector to throttle body elbow lower left side.
Replaced hose. No problem routing it through intake manifold, Pulled the new one with the old one.
Also replaced full load breather hose. Looked good, but the small rubber gaskets were old. Both hoses fairly cheap.
Problem fixed. No more warnings or codes, and fuel trims hovering around zero.

 

I keep seeing folks talking about "Part load breather hose very brittle" What is this hose????? Where is it?

 

On top of the left valve cover near the front.

 

just that one hose others like it?

 

I do not understand your question.

 

Yes, there are several other hoses using this design.

 

how many breather hoses on a 03 Xk8?

 

Here you go: