Hi. Just picked up new to me 06 SC Rover. My 4th RR, first L322. Car was single owner, cared for very well, and runs great for the most part.

I am trying to diagnose a possible vacuum leak. I had a check engine light thrown P0174 lean code bank 2 the other day. I've cleared it and hasn't come back even after going through drive cycle. I followed up with a shop that had it in about 40k miles ago for same check engine light. Must be sporadic.

What isn't sporadic, is idle fluctuation in Drive sitting at a stop light with foot on the brake. I feel like the engine or tranny gets a little louder when I am sitting on the brake pedal and its in gear while sitting at a stop. Peddle pressure feels normal, if not just a touch on the harder side to hold the car from moving.

I've been under the hood to listen for any leaks. I've disconnected and reseated a few of the vacuum lines that were easily accessible and had quick releases on them. The only place that I can hear a faint noise would be in the area of the PCV valve on the valve cover (green circle). Seems to hiss a little. Is this normal?

Also, the little cannister next to it attached to shock tower, which I thought was a vacuum pump, does not appear to be working. At least when I pull the vac line (pink circle) when engine is running, it doesn't appear to be doing anything. I can cover port with finger and feel zero resistance. Is this normal? Maybe its not vac pump but something else.

At a disadvantage because I dont have a full on diagnostic kit. Just cheap one off of amazon. I've watched long term fuel trims, and they seem to be okay at the moment. Nothing double digit.

Any ideas? Thanks for the help in advance! Cheers!

Itza

PCV common point for ingress of air and most likely the cause of your issue (hissing is the dead giveaway), new o rings required or whack a load of extra thick grease on the coupling assembly

Thanks! so is it generally the valve that is leaking (housing), or is it just the connector? Supposed it could be at the junction of valve cover and PCV. I inspected the o-ring on the hose and it looked to be in good shape. Rotating the hose or adjusting it has no effect on the noise. Seems to be coming from internal to the valve (although can't 100% completely rule out hose).

How about brake vacuum booster pump? Is it supposed to be running all the time? Or only when you step on the brake? Thanks and Cheers!