JDM Evo7 with Tephra V7

History:
About 2 months back I got my car back from the mechanic who cleaned the 1200cc injectors which were dialed in by myself a few years back at 1008cc and about 0.8 latency@14V. Prior to that, the car had a middle ruff idle with AFRs swing between 13.7 and 16.1 but spent most of the time at 14.6-14.8 with fuel trims under 5%. After getting the car back, it was 1+ AFR richer everywhere in open loop but closed loop was far more steady. Left it up to the ECU to adjust fuel trims but eventually got a P0170 Error. All the LTFT were -ve max out and the STFT was still pulling.

Current:
With the discovery of the Injector flow rate linearization table I thought it was about time to sort out my idle problems as well. This thing not making any sense any more. The injectors are dialed in at 1080cc with 0.72latency@14V now. Generally it like this setting. The problem is after some driving the Low LTFT is -10% or lower and High LTFT is -6%. Mid LTFT is +1! At idle, the STFT would add 4-9%. I sat in the car for over an hour watching this and it refused to update the Low LTFT. On subsequent attempts to fine tune the injectors, on idle, the afr would drop down to 13s MAX out Low LTFT and the STFT and throw the P0170 error.

The car runs lean on throttle-in but settles back down quickly. AFRs spikes down to and from 12s far to often for daily driving.

Why is it that Low LTFT will never correct upwards but is more than happy to correct 4-5 times within a minute to make things as -ve as possible?

Any help in getting my injectors dialed in correctly and fueling problems would be appreciated.

 

Have you tried decreasing latency, or scaling up a bit more? All of your trims are pulling fuel, so you need to pull fuel in the tune.
Also, check for vacuum/boost leaks first. Doing a boost leak test will uncover any potential leaks that need to be fixed.

 

Yes I was until I realised that I dropped below the stock injector latency and still the strange the swing down to 13AFR was happening. I'll see if i can get a vac test tomorrow. Since I'm looking at a possible mechanical failure, has anyone heard of the stock FPR sticking or failing? seems to me that might account for some of the problems (not the ECU refusing to adjust the LLTFT upwards).

 

I got a chance to swing by my mechanic for a bit. He did a superficial check for leaks but found nothing to match the symptoms. He suspected that the resistor to the fuel pump maybe flaky so we swapped that for a new one but the same thing happened. He wanted to swap the fuel rail with on which had a fuel pressure gauge on the entrance but I ran out of time. He is thinking an injector may be dribbling randomly. Whatever it is I can't even DD the car with the AC on any more.

 

Long story short, it was the O2 sensor.