Something strange happened last night.

I got a little "spirited" while driving on the freeway and had some high-speed fun on my drive home. All of a sudden, after returning to normal speeds, I looked down at my AFR gauge and it was reading 17.5:1 while I was driving straight-and-level at 75 mph. When I started boosting, the ratio dropped back down to 14.7:1 or so (and when I floored it, it went down to around 12.5:1, so that's totally normal). I let back off and cruised and the AFR climbed to 18.3:1. Waaaaay too lean.

While idling, the AFR is just fine. While boosting, the AFR is just fine. But while driving normal at any speed, it wants to run SUPER lean.

Any ideas? I'm stumped.

Do you have the 7th injector with the AFR calibrator? This question would probably be answered alot faster over on customtacos, lots of people with your set up over there.

Ya I think I'll give that a shot. Thanks!

And no, I don't have the AFR calibrator (which in my case would've been the O2 sensor calibrator).

This is definitely something new and weird to me. The only things I can think of are faulty MAF sensor or front O2 sensor, but that's a real shot in the dark. Plus, no error codes. <img src="/forums/images/graemlins/barf.gif" alt="" />

Update:
Now it's running fine for the most part (out of nowhere), but the AFR gauge is showing that the mixture is still jumping around a lot. Definitely not as stable as usual.

Could a bad front O2 sensor be the culprit?

Maybe. How are your cats? Also what type of wideband are you running?

The cat is a Magnaflow hi-flow that I installed about 50k miles ago (it's a 49-state truck with only one cat), and the wideband is an Innovate Motorsports AFR gauge (plumbed into the exhaust tube, just upstream from the first O2 sensor).

I'm taking it into my tuning guy this week to get my muffler replaced (my old Flowmaster is finally falling apart - thank God! Getting a Magnaflow!), so hopefully we can nail down what the issue is. My wishful thinking is hoping that the muffler is so deteriorated that it's backing up the exhaust and causing the truck to run all screwy, but I know that's a long shot! Haha!

Thanks for your two cents, Greg. Always appreciated.

WARNING: Off topic <img src="/forums/images/graemlins/scared.gif" alt="" />
Greg, I just noticed you're running the Supra injectors. How do you like them? That would've been my personal choice (over the URD 7th injector) if I didn't buy my S/C as a whole kit. Do they keep up with the smaller pulley?

Actually, i changed my mind. I got my stock injectors rebuilt and bought the 7th injector from URD, however i will be controlling it with a MAPECU2 instead of the URD calibrator (way better system). Everywhere i've read, the 7th is the way to go with the s/c, so i went that route.

I actually havent built the motor yet, it's sitting in my garage waiting for me to get my winter car back on the road, so i can put the 3.4 in my 4runner. I'll post up build pics next week in the main toyota forum.
Also my buddy had issues with his innovative freezing up and such, is it the innovative or is it your truck?

About the pulley, it can keep up fine. stock injectors are 245cc, so 1470cc total, where supra injectors are 305cc, 1830cc total, and they keep up with the 2.0 pulley just fine. The 7th is 660cc, bringing the grand total to 2130cc, much more than the supra injectors. SO, actually, the 7th can handle more boost than the supra injectors.

Nice! Excited to see the install pics, that's a good project. And a 2.0 pulley?? That 4Runner's gonna be a rocket!

MAP-ECU2 is much better indeed - the SplitSecond program from URD gets the job done, but is too outdated.

As far as the Innovate, I had problems at first with it giving me scrambled readings every once in a while and losing calibration. Turned out to be a loose ground wire. <img src="/forums/images/graemlins/shiner.gif" alt="" />
But, I know something has to be off with the truck itself, because it was running horribly along with the lean readings. Hopefully I'll have it all figured out next week and I can post back with my findings. <img src="/forums/images/graemlins/smile.gif" alt="" />

Well the MAF you can check with a multimeter. I believe the resistances are in the FSM (or you can find it online).
Prob be a good idea to clean it too (electrical cleaner, do NOT touch it but you prob know that).
o2 sensor, you can go to sparkplugs.com or urdusa.com, get an OEM one! (no bosch, but you prob know that)

As for the pullies, im running urd idler, crankshaft and 2.2 ATM (going to break in the motor on the 5 or 7 psi then go to the 9 for this year). BTW there is a group buy on URD crank pullies right now and they wont be producing them again, theyve got them on sale for $250 for i think a week or two more if you're interested.
BTW more updated mod list in my sig now... argh you dont even want to KNOW how much this swap is costing me, but it's going to have the power of an LS1 and be all toyota sooooo.....