Engine Drivetrain 1st Gen Cooper S Most liked posts in thread: P0172 Code

I believe I finally solved my P0172 problem.
I always suspected a small vacuum leak somewhere but could not find a leak.
I finally replaced the plastic hose that goes from the Manifold Pressure Sensor (near the thermostat housing) to the manifold because the code started not too long after I replaced the thermostat gasket.
I also replaced the intercooler boots.
No code since with hundreds of miles driven in various conditions, highway, city, and Auto-X.

 

Thanks guys. I will try a OEM O2 sensor and report back in a couple weeks.

 

Update: I think I finally traced down my P0172 problem. Over the past two months I have swapped O2 sensors, MAP sensors, checked the fuel pressure, and looked at various vacuum lines. I found a loose vacuum line where the Fuel Pressure Regulator (FPR) vacuum line connects to the manifold. Must have been leaking slightly. I replaced the short hose and all has been good so far.

History: About 5 years ago I added a boost gauge which required adding a tee fitting to the FPR vacuum line. To add the tee fitting a used a 2 inch long piece of 3/16" vacuum line to connect to the intake manifold where the FPR line previously connected. Well that short piece of hose was now slightly loose fitting at the manifold barb.

 

I never took it to the shop. Just kept working it myself.

 

I spoke a few hours too soon.
P0172 came back last night. It is like a bad dream.
Looks like a little more investigation for me.
I might even have to break down and take it to a shop.

 

Sorry for the slow reply but I have been continuing to troubleshoot. I first replaced the front NTK sensor with a BMW OEM sensor. That did not solve the problem. I did find and fix a loose vacuum line for the boost gauge and that did not fix the problem. Last week I replaced the rear NTK sensor with a BMW OEM sensor and thought that corrected the problem but after about 100 miles the P0172 code came back on. Thus it was not the NTK sensors causing the code. I suspect there is a slight vacuum or exhaust leak somewhere that I cannot find. Next I will look more closely at the exhaust gaskets.