Lean afr during wot

Iv been battling this weird issue where afr ramps up to mid to high 12s during wot then back down. I also have the infamous hesitation/backfire after shifting form 2nd to 3rd while at wot. When this occurs afrs ramp up to the 13s right after the hesitation. I’m on e25 and fully tuned my tuner says it’s not the tune and he suspects a sticking bpv however I blocked it off and no change. I pressure tested the system from the maf housing back with 23psi and no leaks. Brand new 02 sensor maf sensor and maf o ring. Brand new spark plugs as well. Here are some logs. Anyone ever seen this before my tuner is convinced it’s a hardware issue nothing to do with the tune and I’m stuck at a loss.

 

Instructions:
1. Post a picture of your engine bay, intake side.
2. Also post what your intake actually is and what airflow straightener it has (a pic of the intake with the filter off, looking inside will work)
3. Post an idle log (HOT engine please, preferably after you arrive at work or have been driving twice as long as it takes the coolant temp to get to normal).

If you get the idle log with the hood open, I'll need to know if your radiator fan is on or if it's windy while you have the hood up, though I'm reasonably sure I'm already going to recommend that you get one of these:

https://www.treadstoneperformance.com/honeycomb-maf-mass-air-meter-airflow-straightener/p103828

Having one has saved many a people from headache shit like what you've got going on, even though several tuners say you don't need them.

I run one myself, in fact, and have a spare:

 

Is the new O2 sensor OEM? Is the maf OEM?

 

Yes both are oem. Honestly the air straightener makes a lot of sense. I have a corksport 3.5 intake. I’ll send the pictures and logs when I get home

 

Here is the log there was no wind ac is off and hood is down. Here’s the pics also. I ordered that straightener can I put it right in front of the corksport straightener? I have a 3.5 inch corksport intake also.

 

It will probably stick out a bit but that shouldn't be too much of a problem. Just make sure you gently squeeze the areas that stick out far enough to prevent you from installing it, so it collapses down and does a snug press fit like thing. On mine you can see where I fucked up and squeezed too much, but even with that, it's only in there by friction and hasn't moved in years.

 

Based on what I sent you does that look like my issue?

 

Well there was no wind. Maybe turn the AC on (to force the radiator fan to run) and see if the AFRs or MAFv changes erratically?

 

Holy shit with the ac on maf volt and afr are both rapidly moving up and down

 

Yep. @iamareios had this issue, and the fix was honeycomb.

 

Enki practically saved my life suggesting the honeycomb for my 4" intake. STFT would peg and hold at +25 when the fans kicked on. Now the ecu properly adjusts and STFT comes back down. The car doesn't drive like absolute dog shit now with the AC on! Thanks @Enki

Sent from tapioca

 

Straightener in my CS MAF housing came loose and was moving...had to re silicone it in place, shit I might just remove it now and toss this honeycomb in after reading this thread

 

You really should.

 

So has anyone had afr issues at wot because of this like I’m having?

 

You have issues with just having the AC on....Imagine 100x more wind coming through the engine bay and ask yourself that question again.

 

same thing happened to me a few years back, also with the cs maf housing. I thought my intake manifold had a damn hole in it with how high the LTFT ended up getting before I discovered it was the straightener. Superglued it back and no issues since, probably will upgrade to a honeycomb when I get a bigger intake.

 

Here’s an update. The honey comb fixed weird fuel trims and cruising afr. However it did not fix my lean at wot issue. Car still has 0 kr but it does still spike at wot then comes back down.

 

Yeah it was never going to fix anything at WOT, only lower flows where variability would be higher.
You either need a MAFCAL or to find and fix a leak.