Misfire on all cylinders, P0171, troubleshooting, 04 Cabriolet 1.8T, PCV?
Troubleshooting misfire codes on all cylinders and P0171 (bank 1 lean) on a friend's 06 A4 Cabriolet 1.8t. My initial thoughts were a simple vacuum leak but this vehicle's vacuum system is more than complicated. Engine runs very rough at idle and eventually smooths out when warmed up.
I smoke tested and found leaks at the crank breather tube (it was broken off) and also at the hard plastic pipe from the 3 way tee below the intake manifold. I pulled the intake manifold and replaced the tube and ran new rubber hose with elbows and clamps and tested again, all good.
I am having trouble locating the actual PCV valve (if it has one).
RockAuto lists the below item as a "pressure control valve":
https://www.rockauto.com/en/moreinfo.php?pk=1191415&cc=1432683&pt=5052&jsn=1611
RockAuto also lists this as a PCV and other sites refer to it as a crankcase breather valve:
https://www.rockauto.com/en/moreinfo.php?pk=11271212&cc=1432683&pt=5052&jsn=1607
I am wondering if the actual PCV is stuck open and this is causing a lean mixture at idle.
See the attached photo.