A4 2.8l P0174, pending P0150

[Phishnvdub]

01 A4 2.8l. Just finished doing the TB and components this week along with complete PCV system, VCGs cam caps/seals, tensioner seals and vacuum lines. Very stoked as there are zero oil leaks and car seemed to run great. When I drove it the 20 mins home two weeks ago it was leaking oil pretty bad and when I got to the driveway at low RPMs it was running rough. Figured because of oil leaks getting into plugs. Bank 2 plugs were black and sooty. Other side were just oily.

Two days ago I drove the car putting about 40 miles on it and ran fine. Yesterday after driving about 10 mins it started running rough at low RPMS almost stalling. Set the P0174 code and Po150 was pending. Both to do with Bank 2. 174 running lean and 150 O2 sensor malfunction I think.

As soon as I cleared the code while car was running it smoothed right out. I have an ultra gage hooked up. Doesn't do a lot but can read O2 voltages. I notice when car is cold. The rear two do pretty much nothing. No fluctuation. The front bank 1 is working but the bank 2 front is not really doing much. If I really knew what to look for or what the numbers meant I could give a better description.

Am I pretty safe to say that front bank 2 O2 sensor is prolly shot causing bad reading and making that bank run lean and clearing the codes resets monitors so all is OK until the monitors are ready again? When I finished the TB belt job I had to clear a code because forgot to plug rear cam sensor in. So after driving a while maybe it's why it started acting up yesterday until I reset codes again?

[Phishnvdub]

Small update. After resetting codes the other night and researching what normal 02 and MAF values are when running. Everything seemed to be fine. Idled more normal, and 02 voltages looked pretty good.

This morning I changed plugs out and idle is much smoother and O2 readings look even better. I drove about 60 miles today, got all 8 monitors ready and still smooth. I thought as they started to pop things were going to get rough again.

Before I did the TB, PCV and VCG stuff oil was leaking from what looked like everywhere. Crappy VCG job, horribly taped up PCV lines along with the pump and big Green check valve being clogged. Plugs were really oily from the leaks. When I finished fixing everything I just sprayed the plugs out and cleaned them up. I am hoping that wasn't good enough and caused these idling and CEL problems. Just need the rear coil springs to come in to replace the broken ones in the rear and hopefully can get this car inspected. May return the O2 sensor I did not install also. My luck as soon as I do, things will get wonky again.