Installed a Short Ram Intake setup in a 2016 Mazda 6 2.5L, basically a replacement of the stock air intake system and I am now getting a P0101, weird performance stuff, and weird fuel trims.

Fuel Trims: LTFT -8%/-10% at idle, -14%/-18% under acceleration, -5%/-9% cruising. STFT 3%/7% at idle, pops up to 30% when the LTFT goes down to -14, oscillates weirdly at high levels when accelerating sometimes.

Mass air flow oscillates around 1.9-2.3 g/s at idle, is this too low for a 2.5L engine?

The car hesitates when accelerating out of a turn sometimes, like drops 1k RPMs for half a second or so. Mostly happens when turning or accelerating when the engine is pretty cold.

Already tried: Checked for vacuum leaks, cleaned MAF sensor, reset ECU several times after every change.

The tubing is the same dimension around the MAF sensor as the stock airbox is where the sensor is, so that shouldn't be the issue (I think). Kit is from Protuninglab, link: https://www.protuninglab.com/20ma62l4hesh1.html

I noticed the P0101 pending a few times on cold starts but it usually resolved itself after driving for a bit. Car is a 2016 Mazda 6 2.5L I4 SkyActiv naturally aspirated. I like the sound of the SRI so would love to keep it if possible. Any ideas?

  • When LTFT is negative, it means that ECU has detected less air is entering the engine and it has reduced injection of fuel to keep air/fuel ratio constant. If you had Vacuum leaks, your LTFT would be positive. I think you need a professional ECU reprogrammung if you want to keep the SRI. Have you checked your fuel trim at mid to high throttle positions? Jan 24, 2022 at 8:22
  • 1
    Have you tried returning to stock to see if the issue goes?
    – HandyHowie
    Jan 24, 2022 at 11:24
  • What was the air flow with the stock intake? Using a known stock setup and measuring airflow values lets you see before and after effects mods. Some vehicles have issues with aftermarket intake systems with the maf sensor being sensitive to any disruption in airflow resulting in strange issues. The maf and map sensors are critical to EFI systems. As suggested, put the stock intake back and measure/assess changes, presuming the problem goes away, pointing to the aftermarket intake being incompatible with your engine.
    – F Dryer
    Jan 25, 2022 at 1:42


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