I am trying to track down a vacuum leak causing P0171&P0174 codes on a 2003 XKR. There is a stainless steel looking pipe that runs down the underside of the supercharger on the left side running front to back. Near the front of this pipe, there is a schrader valve on it with a blue cap. Right in front of the schrader valve, there is a fitting and a hose coming off the pipe that runs to the center of the motor and then down. My short term trims drop from + 14 to -7 when I spray carb cleaner on the fitting coming off the stainless pipe and into the hose. I thought the hose may be loose, and when I pull the hose back a bit I see it looks like this hose is covering a black metal collar or pipe. Im not sure if this is a hose or a pipe. I can`t find this piping and hose in JTIS.
Can anyone tell me what this pipe is and how to go about fixing this leak?
Thanks!

 

What you describe with the schrader valve should be the left side fuel rail. There is a hose that connects the right side and it runs from the front of the left side rail down under the front of the S/C to the left side, also like what you are describing.

If that one was leaking such that spraying carb cleaner on it would change something about the fuel trims you would also have a fountain of gasoline to contend with.

Try checking the on the right side fo the S/C outlet, toward the back bottom. There is a nipple in there that is supposed to feed the fuel pressure regulator. The hoses can get old and slip off easily. it is also a common diagnostic procedure for checking the regulator to pull it off. It is in the same general area as where you sprayed and could be how the fog could get into the intake.

 

Yes...I just came in from looking again and you are right...it is a fuel rail. I`ll check the fuel pressure regulator as you suggest. I don`t have any gas leaking.

 

CFULTON...you have made a Merry Christmas for me! I checked the fuel press regulator and sure enough..the 90 degree elbow was attached to the regulator, but the line was dangling free. I have been looking for this leak for a couple of weeks now. Thanks for the great suggestion, it solved my problem.

 

The spray onto a fuel line would not cause the reaction you are getting what I would say is that you are close to the problem. Remember fuel is pushed to the engine by the fuel pump/pumps in the tank a vacuum leak is pulling in ambient air. The vacuum is sucking in the TB cleaner into the engine making the change you are seeing. I would say you are close.

I see you found the problem.

 

Glad it was that simple a fix.

I had something similar and just like yours, crazy high fuel trims at idle but perfectly normal looking at other load levels.