Fk8 AFR hunting / oscillation

[SpicyRat]

Compression test this coming weekend. Will post results.

[SpicyRat]

Compression test yielded a perfect 150 across the board on all cyls.

[SpicyRat]

159/160 across all cylinders. So no vac leaks, no bad sensors, no blown engine...what's next Hondata?

[Hondata]

Put the stock intake on.

[SpicyRat]

Stock intake is on. It attenuates the issue. Anything else besides that? If you have nothing else to offer, I understand.

[Hondata]

I think I mentioned this near the beginning - it seems like you have narrowed the cause down by yourself.

[SpicyRat]

Narrowed down to what, a phantom? Voodoo? Sorcery? Sounds silly, but the Tuner and I made it to the end of the flow chart with no more flow (if this, then that) scenarios and also no result.

At this point we are adding to the diagnostic process for others to build off of in this apparent NFT scenario and we are asking for critical thinking input as brainstorming is very helpful. But saying "put the stock intake on" after all of this tedious testing and data sharing, knowing stock intake doesn't solve anything, is a strange way to brainstorm.

Next step is to pull the VC and smoke it to see if there is something like a crack in the pcv under the VC. I'll also check all mechanical timing marks, check for any other witch hunt trails or clues, and hopefully unmask a familiar character who was the villain all-the-while.

Either this is a one of a kind anomaly that no other FK8 owner has ever experienced or this happens but people are not aware for various reasons (including incomplete diag solution charts).

Just to be clear, the goal is to run the HVI w/ Race MAF for future endeavors with the car. Putting the stock intake on or putting the carbunder a car cover indefinitely won't solve the issue.

[SpicyRat]

We have run tunes with the primary O2 disabled, the secondary disabled, both disabled, cat cycles disabled, all ports on the PRL intake plugged, all ports wide open, bypassed bypass valve, bypassed bpv sol, pcv venting to atmosphere, pcv plugged. We've pressure tested to 18psi the entire motor; from the stock Honda turbo inlet through the head. We pinned out O2 wiring, checked for compression as per the FSM, New OEM spark plugs, Installed new MAF, new primary O2, and new ACT is on the way. That way, all closed loop sensors will all be new.

The only thing that have not been done is 1. to change out the injectors. Simply because an injector issue would lead to a misfire somewhere, especially WOT. And changing a MAF doesn't cause an injector to leak more or less in that moment. And 2. Buy a new ECU to see if there is an issue in the manually jailbroken ECU that traces back to Ktuner.

[Hondata]

See this post viewtopic.php?p=122784#p122784
- lambda, cylinder charge and fuel injector variation are the same as a stock vehicle
- using the non stock intake makes things worse
What are your expectations?

[SpicyRat]

So you're saying that all the data I have shared is what all fk8 owners with downpipes and racemaf PRL intakes experience?

[Hondata]

What are your expectations?

[SpicyRat]

Well, beyond what has already been discussed, here is a screenshot of another FK8 with the same exact mods under a screenshot of mine. PRL Racemaf as well. Only, the AFR doesn't oscillate as violently as mine does.

This fk8 is tuned by the same tuner and was running the same tune as I was.

So that car's datalog is a desired outcome.

Thoughts?

[Hondata]

The -9% long term trim indications somethings is quite different. There are two approaches. 1. Test / change items one at a time until you identify the cause. 2. Start from a stock configuration and add modifications one at a time until the problem occurs. Seems like you have already tried a large number of things and I'm hesitant to offer suggestions that require a lot of work on your part, but that would be my approach.

[SpicyRat]

This was another revision we tried. The issue is not MAF scaling related.

[SpicyRat]

1. Test / change items one at a time...

Perhaps you can help with this info I got today:

If I unplug the MAF while the car is running, it'll chug/stall.
If I unplug the ACT while car is running, the AFR goes even more irratic.
If I unplug the MAP on the charge pipe...nothing changes. Except for triggering the check engine lights.

The boost/vac reading stays the same, fuel trims stay the same, it's like nothing happened...

Is that supposed to be a thing or have I come across a potential cause for this nonsense?