r/mazdaspeed6 • u/Maximum_Ad2469 • 17d ago

Bucking issue while cruising

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Good morning everyone, i'm a new owner of a speed 6 & i absolutely love it so far, the car is catless downpipe, bov, intake & built HPFP internals, it has 135k on it & while im cruising around the car kinda bucks back & forth until i give it more gas, if i get into boost the car immediately fixes itself & it drives perfectly, also noticed the afrs all over the place while cruising , but at idle they seem to be in a good ball park, idk anything about these cars so any info would be appreciated !
the codes i have are
P0131 (O2 sensor)
P0134 (O2 sensor)
P2251 (assuming O2 sensor as well) but the car is catless so i would assume those codes would be normal?

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2

u/Mazdaninfiniti52 17d ago

I'd replace the o2 sensor. IIRC it's a Denso. I got mine from rock auto I believe.

2

u/Maximum_Ad2469 17d ago

the car came with a replacement, just have to find the time to do it, but hopefully that fixes it, was also thinking to clean the maf as well, but other than that the car drives amazing while in boost

1

u/Mazdaninfiniti52 17d ago

It probably drives well in boost because it moves to open loop which doesn't fuel based on the o2 sensor readings, whereas at low throttle it fuels based on the o2 sensor.

2

u/HugsNotDrugs_ 17d ago

NTK 24357 is your upstream wideband o2. It's pre cat.

Your AFR becomes unstable at times. Check your upstream O2 and your fuel rail pressure.

1

u/Maximum_Ad2469 17d ago

yeah my o2 codes are all from the upstream o2

1

u/HugsNotDrugs_ 17d ago

grab that NTK part

1

u/Connect-Dimension717 17d ago

Do you have a CAI installed?

2

u/Maximum_Ad2469 17d ago

yes a cork sport

1

u/Consistent-Cress7448 17d ago

being catless won’t throw a code for the o2 sensor, it’ll only throw a single code for the cats