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Discussion Starter · #1 ·
On my zombie Evo X, I just rewired the front O2 sensor, and to my surprise, it seems to work most of the time (after the car has warmed up at least). However, the pig still runs rich as hell at idle. BUT, I know it's working, cuz when I lay on the throttle a little, it snaps to 14.7, which it absolutely did not before (I made sure to re-enable closed loop, don't worry).

My understanding was that at idle, the O2 sensor(s) was 100% responsible for AFR. Do I have that wrong?
 

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Discussion Starter · #3 ·
Do you have any modes done. Fuel pump, fuel pump hanger, injectors etc....
Almost nothing OEM, except for the fuel rail. Working on the fueling has been trial and error up until now.

I've been working on MAF scaling and stuff, and I have that going ok. But going from LTFT low to mid causes a big slingshot, and low doesn't seem to want to budge, so I'm wondering if there's anything else that affects low. I'm gonna reset my fuel trims again and see if that helps.
 

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Is this a fresh tune or are you just tweaking it?

You should calibrate a good MAF scaling with the stock injectors (and stock injector settings (ie latency, scaling number, low-pulse-width adder, etc)), and then calibrate the aftermarket injectors.

Or, if you have a known good injector calibration, then you can work on the MAF/MAP.

Trying to do both at once is not advised.
 

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Also, to answer your question:

My understanding was that at idle, the O2 sensor(s) was 100% responsible for AFR. Do I have that wrong?
You're half right. The front O2 will provide feedback on how the other fueling and load tables are doing. The load is calculated via MAP/MAF, and the fueling is calculated based on Load, Injector Latency, Injector Scaling, Calibration Fuel Map, and a few others.

In closed loop (ie when the front O2 is doing its job), the ECU will use the STFT + LTFT trims try to hit 14.7 by either adding or removing fuel. If your LTFT trims are way off, then you need to adjust some other tables.
 

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Discussion Starter · #6 ·
Is this a fresh tune or are you just tweaking it?

You should calibrate a good MAF scaling with the stock injectors (and stock injector settings (ie latency, scaling number, low-pulse-width adder, etc)), and then calibrate the aftermarket injectors.
Yeah, unfortunately it was built up from nothing but a crankshaft and a head, so I'm doing it all at once. I have taken someone else's voltages/latencies for the same injectors, and I've copied the MAF scaling for that specific intake online. Other than the idle, it runs pretty good.

To fix a wonky idle, would I be tweaking the bottom end of the MAF table, or is there another table I should be looking at?
 

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What's your Load at idle? Which injectors do you have? What are your Low/Mid LTFT trim values?

Several tables could create rich idle AFR... eg too much latency, too much MAF or MAP, too little injector scaling.
 

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Discussion Starter · #8 ·
What's your Load at idle? Which injectors do you have? What are your Low/Mid LTFT trim values?

Several tables could create rich idle AFR... eg too much latency, too much MAF or MAP, too little injector scaling.
Load is about 21 cold, 30 when warm. I really need to recheck my logging setup, but I'm at work for the rest of the weekend; looks like LTFT low is plastered at -19, and mid is 0 (🤔).

I'm running ID1050 injectors at ~960 iirc.

I've attached a log, if that's worth any extra info. If anything obvious stands out, let me know and I'll try to grab a 10 minute log on my way to work.
 

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