Hello guys! I had some minor problems with my fd for a while, or I think its a problem.
everytime I start my car up, i'm reading around 11-12 AFR while warming up/ idling, which is normal for my build
and when I start driving her for around just 5 minutes, my afr would spike to 16-18+ while driving. which is insane, I'm still hitting boost perfectly fine (10lbs)
I checked my fuel pump at first, a connection from the battery to my fuse looks a bit burnt (I have the relay mode for my fuel pump)
, i've replaced the wire just incase that was causing an issue of shorting/ or not powering the fuel pump enough for the car.
still the same issue.

I'm wondering now if its my fuel filter thats maybe bad/clogged, (i've replaced it 3 years ago, but driven only 4-5k miles)
or is my AFR reader just broken? Or what else am I overlooking that could cause this?

car runs fine, idles fine, and boosts fine

my mods are single turbo, vmount, halfbridged,

Thank you!

 

It could be your tune. But regardless, I'd suggest installing a fuel pressure sensor so you could know how your fuel system is acting.

 

mm I see, maybe I need a retune? I've had the same set up for about 5 years after my full rebuild, and got the same tune since then, is it possible the tune needs to be updated since its been so long?
also forgot to add, my fuel pressure is reading 40 PSI as normal

 

To clarify - you get 16-18AFR during cruising only or during boost/hard pulls too? Tune wouldn't go bad by itself unless you make some changes to your setup.
Might be your oxygen sensor is bad and acting on you..? Important thing is make sure your fuel system is fine, and best way to do it is logging fuel pressure when driving, then analyzing the logs afterwards.

 

Cruising is around 16-18, hard pulls im getting 15-17 which is still not good, my normal range was 12.8-13.5 with hard pulls

even then, my boost is still perfectly fine, same with driving, cruising and idling is all perfect, all the way down to starting the car.

so it might be my sensor then you think?

I will have to check the fuel logs for sure, I have a POWER FC, isnt there a way to check logs on there in real time if i remember correctly?

Thank you again

 

I don't believe the power FC is particularly subject to corruption via noise. I'd suspect either a supply issue from filter/pump failure/wiring fault or you are getting a misfire as a result of a coil/lead/plug starting to fail.

 

I changed my spark plugs, + checked compression before doing so, I religiously change my plugs out every 4-5 months even if i don't drive that much, everything checked out fine, and plugs were all in perfect condition when i pulled the old ones out.

so far my car seems fine in all aspects, whats freaking me out is just the AFR has been acting up like this for about a week, but my motor/engine sounds perfectly fine + it hits boost fully. I never had an issue with my afr gauges before on my other cars, it just seems weird that when the FD does start, it idles around 11-12.5 AFR but once I start driving, it says its "leaning" out way too much.

 

What WBO2 sensor/controller are you using? And how old is the sensor?

15-17 afr under boost should absolutely be resulting in knock.

I would look to a fault in your o2 sensor if all else seems fine.

(edits to correct spelling/words due to phone swiping)

 

Yes I would think so.. I hit boost about 3 - 5 times a drive since this happened and no fault in my car. everything feels and drives fine

I have a AEM AFR Gauge, it is about 4-5 years old, I got it the same day as my rebuild, the 02 sensor is attached right ontop of the front pipe, i can access it when i open my hood
can it be that it finally overheated and is giving weird readings when im driving due to heat?

 

^Ding. Ding. DING! Pull your sensor, and look to get it replaced depending on its physical condition. (Post pictures)

In short, your engine likely wouldn't be surviving "3-5 boost runs" short-term if you were truly at AFRs north of 15 during said boost runs.

 

02 sensors can wear out quickly, especially on a rotary with high heat. Further compounded by the fact that most are placed within a few inches of the hot side of the turbo.

I would replace the sensor to start and see what that yields. I would also suggest relocating your sensor closer to the DP/MP connection.

I *think* the instructions for sensors mention 18" way from turbine if I remember correctly.

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I agree with the others that said it's probably your WBO2 sensor or controller. Another possibility is that the WBO2 sensor may have loosened up slightly, creating a tiny air leak into the exhaust stream - I've had that happen once on my FC, the symptom was lean AFR readings at all times while the engine was otherwise running fine. Tightened up & torqued the WBO2 sensor to spec, and AFR readings went back to normal.

 

I agree with the sensor check, my AEM sensor would read correctly intermittently when it was going out and the hotter it got, the less it worked so it would usually work OK during the first part of the drive but then would totally read incorrectly.

Aside from that, if you have the ability to install a fuel pressure sensor and put a go pro or something under the hood to see what the fuel pressure is doing as the boost rises (I wouldn't run the car hard until you get this ironed out) just to make sure fuel pressure is rising with boost as it should. If it is not, then you can start looking into the fuel system, plugged filter, bad regulator or pump dying.

 

Hopefully, it is just the O2 sensor but I'm curious...
Was your ecu tuned to that engine setup? Which ecu are you running? Who tuned it?

 

That's far too close for longevity. 18-24" is generally reasonable. Depending on the LSU you're running (4.2 or 4.9 - I forget what AEM uses) element may be marginal at that range however the hexagon has a max temp of 530c, roughly half of the element.

 

+1. Having the 02 that close without a recessed bung will cause it to fail prematurely. I would have a new bung welded at the bottom of your downpipe or start of mid-pipe for longevity.

Eric

 

Appreciate all the input guys! I ordered a new 02 Sensor, will update once I change it!

 

It seems as though even the OE O2 sensor on a close-to-stock, mostly driven on the street FD starts to fail by giving lean readings. On my close-to-stock FD, I replaced the sensor at 57K miles, and the idle speed increased plus it idled smoother indicating to me that the new sensor read richer, causing the ECU to lean out the mixture.

Related thread: http://www.rx7club.com/showthread.ph...condary+sensor

 

I also think it's your o2 sensor. It's too close to the turbo and is being eviscerated by the high EGTs. I have mine right at the tip of the midpipe as do most other people running a wideband. Plug the existing bung and relocate your sensor or you'll just keep eating up o2 sensors.

 

UPDATE!

It was the 02 sensor, it lasted me about 5 years even though it was super close to the turbo
I replaced it and now I'm reading the correct AFR

Thanks everybody!