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A little background: In early october I popped a P0174(lean bank 2) code. Cleared it and drove for a week until it came back on. Cleared it again and it came back in another week and a half. Gas mileage dropped drastically(from 21 to 15-16MPGs). After about 3 weeks of this I took it to a shop to have an exhaust leak test and diagnostics test done. Shop told me exhaust had no leak but my MAF was no beuno. A while back I had stripped the screws that held the MAF to the housing so I had to duct tape it on to keep it sealed. This temp fix was starting to fall apart and allowed a vacuum leak at my MAF. I replaced MAF and so far it seems as if this may have fixed it. I am not 100% sure yet but MPGs are significantly better - just not sure they are back to where they should be yet. After a few tanks of gas i'll know.

In the mean time I figured it was a good time to order a wideband A/F kit. Took the time to figure out that fiasco this weekend but got it all working. Boy was it a hassle wiring this thing up to an automatic new edge.

At idle I am seeing 13.7-14.5 A/F. Partial throttle varied a lot, anywhere from 14-18 A/F. Cruising at 75 MPH saw 14.5-15.0 A/F. WOT saw 11.5-12.0.

Everything seems fine and doesnt look lean to me at all. I only have questions about my partial throttle A/F - is it normal while driving around at low speeds(such as in a parking lot/neighborhood) while feathering throttle up and down to see these jumps up to like 16-18 A/F?

My understanding is that 11.5-12.0 A/F WOT is relatively conservative. With 13.0-13.5 being on the risky side.....is this true? Any certain A/F you never want to see with any setup regardless? Obviously 14.7 or higher but....you know what I mean.
 

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Part throttle can be pretty lean when no load is applied (14-17afr) and idle too is really lean because in these situation theres no load and not a lot of airflow. The only real thing you dont want to see is anything above 12.5 when you're WOT, especially at higher rpm.
 

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Part throttle should be between 13.0-15.9:1 if the front 02's are working correctly and the tune is good. Part throttle meaning anywhere from 10% throttle to 50% throttle. It's should NOT be fluctuating between 14-18:1 18:1 is more than 25% out of range. The PCM can only adjust for 25% over or under the 14.6:1 commanded A/F ratio. This is where your lean code is coming from.

An exhaust leak before the factory O2's (header flanges), or a leak really close after can cause throw off O2 readings (leaner).
 
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