Lean sometimes at idle and under load, failing o2?

[GSLENK]

Final update:
After chicking everything but the plugs/wires, it turned out to be plugs and wires. I am using NGK V-power Copper temporarily (BPR6EY, part#) until I get some BP7ES. got a tad better with plugs, back to perfect with wires. Too bad they are only blue and not red


Original Stuff:
I let my car sit for a few days while I was fabbing an exhaust. I start the car, feels normal. Go for some pulls and I get pretty bad stumbling as boost builds. Then the idle seems a bit off, It will stumble a bit at idle also. I haven't had time to log yet, but It appears the stumble is caused by a lean condition. The car never goes too rich.
Idle is mostly around 14.7-8 and then bumps to 15.6 momentarily with the stumble.

I checked a few things, Fuel pressure is good 37psi , spark plugs are fine (I believe a spark issue would cause rich conditions right?)

Fuel injectors were running fine before and they all click when energized.

I just replaced the fuel filter to be safe.

My last BLT was good as of 2 weeks ago (no mods at all since then).

So i guess it down to one of 2 things, o2 sensor on its way out, or my injectors are weird (I think they rarely go bad right?)

Would a failing o2 sensor create these conditions? (it is mounted in the factory o2 spot, and been there for about 6 months to a year)

Would a log tell me if its going bad?
And what else could I look for?


HERES A LOG: starts acting up around 600 seconds. from a cold start all the way through hot idle.

 

[PANDARESCUE]

Easiest way to check if your o2 sensor on your wideband is bad is to pull it from the exhaust and wrap it in a fuel soaked rag then watch the guage it should go full rich and stay there if its bad it will go full rich then after a few seconds go full lean

 

[GSLENK]

yeah its not the o2. I replaced it just in case. still does that thing where it gets lean. I think its time to test injectors...

 

[brownfinger]

I would say it's the fuel pump. It can hold the correct pressure at idle, but not deliver adequate volume. If all your fuel trims are maxed-out, but everything else is OK, it's a safe bet that you need a new fuel pump. But do a BLT first.

 

[GSLENK]

Just popped in a new 255 a few weeks ago fuel trims are not maxed out.

Just now, I swapped to the original 450s, no change.
I swapped to a new o2, no change.
I had replaced the fuel filter, new change.

I volt-metered at the FP wire (its a rewire) even during the sputtering I am getting 13.7 volts constantly (sputtering or not).
BLT results are great, no leaks.

Anything else it could be?

Coolant temp sensor?


The only thing that changed from good running to poor running was: One day I decided to build an exhaust. The car sat for 3 days while I fabbed it around work/school time. Finished, took a spin, terrible loss of power and lean conditions. Before that, I was making really strong 19psi pulls.

heres a new log, after swapping in good old 450s, and the new o2

And heres a vid...
No rpm surging (so its not a leak)

only lean spikes.

my intuition says it cannot be injectors or coolant temp sensors... but the coolant sensor seems like the only next logical step.

Car runs pretty good in open loop during warm-up. This is at operating temp around 196-200*
http://www.youtube.com/watch?v=sKieqeTSoJo&feature=youtu.be




AFTER A LITTLE MORE research... I think it may be the plugs since its not injectors... Ill try some new plugs since a Wideband will read lean because of a misfire since there is a ton of oxygen in the cylinder.

YUP, it was plugs a little too fouled. could only find bpr6ey locallyso ill be ordering bpr7es asap.