Hey guys, like the title says. Bank 1 too lean, as well as an AWD code which I’m pretty sure is just being thrown on safety mode because they turned on the same time.

From the research I’ve done, people are speculating O2 sensor, plugged cat, or vacuum leak. I don’t think it’s a vacuum leak because I looked around and didn’t hear a hiss. Any advice on where to start?

I did see some wet hose as if it’s leaking a bit of oil, not sure if it’s PCV valve? It runs from the inter cooler area to the intake pipe after the air filter. Photo attached.

 

Thanks in advance

 

Changed spark plugs with OE laser iridiums yesterday. Had a good look at all vacuum lines with the intercooler removed and didn’t see anything glaring as a leak, I.e. no cracked or otherwise faulty lines. Code reader saw normal voltages for the o2 sensor(.5-1v).. going to get fuel system cleaner today to hopefully clear out a clogged fuel injector if that’s the problem?

any insight or troubleshooting tips, please, don’t all jump in at once. This one kind of has me stumped and I’d rather not throw hundreds at it to guess and check. Thank you!

 

I'd say pull the MAF and clean it - won't hurt. Could also be low fuel pressure - clogged filter or pump on its way out. Upstream o2 sensor is also a possibility, but I think those very rarely fail. A downstream sensor would probably throw P0420, so I doubt it's that either. Any actual symptoms while driving the car or only the codes?

 

Forgot to mention this car has almost 220k miles so not exactly super new.

there is a bit of a stutter, especially after the CEL comes on. Also seems to be slightly low on power but not dramatically so.

I’ll try cleaning the MAF with some carb cleaner and report in.

 

Just to give any future searcher an update, seems like fuel injector cleaner seemed to do the trick.

about halfway through the first tank with redline fuel system cleaner the light turned off and hasn’t been on since and it’s been a couple weeks now. Earlier if it went off it would come back on within a day.

MAF sensor appeared clean but I got it good with carb cleaner anyways but seemed to have no effect.

At the end of it all, the work I did was;
1. Intake filter
2. Spark plugs
3. Slightly lube and tighten gas cap better each time I fueled up
4. Cleaned MAF
5. 2 tanks worth of fuel system cleaner

Either a mix of a few of these or just a clogged fuel injector appeared to be the problem.