Fueling problems
 

So I'll start by saying I'm running off a speedyefi speeduino, not a MS, both use tuner studio and are pretty functionally similar, and I had no idea where else to ask these questions lol

So I'm having some interesting problems with my car right now that has left me and my tuner confused and I wanted to maybe get some extra brains on the issue and see if we are missing anything super obvious.

In essence the car is very inconsistent with it's fueling map, on one start it will run 'perfect' afrs from cold start to full boost. It basically runs exactly as I want it to. Then if I shut the car off for a min or 2 and start it, it will run 2-3 afrs richer or leaner, and it appears to affect the entire fuel map, so if it starts and idles 2afrs richer, it will also hit boost 2afrs richer or vice versa with lean conditions. All within the same external conditions ~5°. On top of this I also have a intermittent misfire at idle that'll get worse if the car hits boost it seems. It doesn't seem to misfire under boost, but when I go back to idling it will misfire a bit.

So those are the problems I'm having and here's some more info that may help. I had those problems previously to replacing my injectors, but in case it matters I recently swapped over to some rx8 yellows that I personally pulled from an rx8. The spark plugs are new and gapped correctly (.36) and I've swapped out to a known good FPR and Coil pack. I'm running 91 pump gas, and the tune was made with that in mind. The fuel filter was replaced maybe a year or 2 ago, but as far as I'm aware the fuel pump is the stock unit.

The next step I'm taking as of right now, is I'll be testing the fuel pressure when I get home to see if it is consistent, if it is consistent I'll truly be lost as to what the problem could be so any help at all will be appreciated. Oh and the car is a 1996 1.8l.

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What is your IAT situation like? Is it heat soaking?

I've got the iat plugged in right before the throttle body, right under the iacv, from what I remember I dont think it is. However I'll give it a look the next time I run the car. For iat density we've got it set to 100 across the graph till we have the base fuel table set, would that contribute to this? From what I understood that'll be a fine tuning tweak after everything is mostly set

Probably not a whole lot. But depending in your piping and intercooler setup, your air might be less dense until everything cools back down under motion. Are you able to pull a log idling to see what was different before and after the car sat?

I haven't taken a log yet, but I can and will when I get home, hopefully I'll be able to get it, like I said it's pretty inconsistent. Sometimes it will start off with a super rich condition, all the way through warmup running 2 or more afrs richer or leaner than what it should be. I think I should've specified that as well. I'd say 70% of the time it will startup and run and idle properly, and the other 30% or so it will start with what feels like a riched out or leaned out map.

Take a log during one of those 30% instances. We can see if it’s tune related or something else.

Ok so I got home, hooked up a fuel pressure tester and found my fuel pressure seemed consistent other than when I would give it a quick rev, the pressure would droop before picking back up to 35ish psi and holding there. So on a rev it'd pick up to 45+psi then droop to 30ish and then come back up to 35 and stay there. Not sure if that's normal but figured I'd report it anyways.

As for the inconsistent idle and afrs I think I may have found the problem. I'm trying to touch bases with my tuner just to see what he thinks but I figure I'll post here just in case.

So basically I took a datalog of a cold start and noticed that it looked like the ECU was referencing a afr target and was trying to adjust the afrs to match said target. Which I felt was super wierd as I wasn't running autotune, so I did a little bit of digging and came across the ego correction settings. Now I'm a complete tuning novice so I might sound stupid saying this but I believe the car has been making ego corrections off a base afr map that I don't think myself or my tuner touched.

considering there's no tune or log attached in this entire thread, it's a mystery as to why we didn't find that earlier.

Fair enough curly, sorry. Here is a the data log from a cold start, till around 160clt with some warm starts thrown in at the end, as well as the tune. After 3 days of cold starts it seems ive only gotten the rich map, which is kind of unusual, but kind of welcome if im being honest. If the fuel map just needs to be leaned out everywhere or my injector deadtimes need to be adjusted I can do that. But ya, any insight yall can give me will be appreciated.

Ive got another cold start log from today, and a log for the misfire that ive been getting at idle once the car has been fully warmed up and hit some boost.

So I see in your log, the temp starts out at 59F and at 11.6AFR. As the engine warms up, the AFR rises into the mid 12's with the temp going to a maximum of 154F.
I am running very slightly leaner in my car, but it is really dependent on how the car runs. When cold, the car will likely run very poorly if you attempt to run at 14.7

Once the engine warms up however, you should be able to get it to run well at 14.7. FWIW, I set my AFR targets to 14.7 up to 70map.
Under the AFR/O2 tab, you have fuel correction set to occur at over 316F and 1200rpm. So the Arduino will never try to correct fuel.
Change that to 170F and maybe 800rpm. I would increase your idle duty cycle to bump up your idle rpm, at least until it is tuned. (740rpm idle seems low to me regardless)

Set up a gauge for EGO Correction, so you can see how much fuel the Arduino has to add or take away to get to the AFR target. That will tell you how
far your fuel table is off. Once the fuel table table is correct, you can adjust the cold start settings to get the car to run right during cold start.

On another note, I see that Tuner Studio is showing options for Fuel and Oil pressure. Are these the 2 spare inputs listed on the fishdog website?
I presume you have the fishdog cpu? I am impressed with the amount of stuff packed into this thing for the price. very nice.

I just went with the PnP kit they offer. Im pretty sure it has the fishdog cpu though. As for the rest, itll be a great help! Thank you! I've been in touch with my tuner and we are going to try a few different things and see if we can figure out why its misfiring after being under load. Now that the car seems to start and idle at consistent afrs, we can just lean out the map a bit and be done with that. Ill eventually set up ego corrections once everything is dialed in, I had a misunderstanding of how it worked and jumped the gun on my presumptions. Your description and how my tuner described it basically ruled it out for me. The tuner seems to be leaning towards it potentially being a faulty cas.

Well, We ruled out the cas now as I was able to get it to start misfiring, and I locked the timing to 10degrees, and watched it with a timing light and it still misfired. So the current problem ive got is the car just wants to misfire at idle after hitting boost. Going to swap back to my original injectors to see if it stops. Tuner seems pretty convinced the Rx8 yellows are the culprit here. Heres a driving log with some spirited pulls and also one for the hot start and drive about 5 minutes after the first drive. If you notice in the hot start it oscillates hard for the first min or so before evening out to idle at a higher afr than whats currently 'normal' for the car. But after driving for a few minutes it goes back to idling at 'normal' afrs again. In the second log, its misfiring at idle basically the entire time. I dont feel any misfires above idle speeds, not necessarily saying it isnt there, but Im not feeling them.

Well today was fruitful. Long story short we determined it was the rx8 yellows. I swapped back to the original injectors and the misfire went away immediately. I then took the car out with the original injectors(maxed out at 5k rpms lmfao), got it nice and warmed up and had no misfiring problems. Took it back to the house and swapped out the Stock ones for the yellows, swapped the settings to fit the yellows and it was immediately misfiring badly again. I went ahead and put in an order for some FlowForce 640cc injectors and a dw200 pump. Let it be a warning to everyone who reads this, rx8 yellows used to be a good, cheap and reliable way to go with injectors. Not really the case anymore, real ones are old now and for a rebuilt set you are looking at near the cost of the FF injectors anyways. Take it from me and just get the good injectors off the rip.

Hint: This is why everyone everywhere all at once is telling people never to buy RX8 Yellow injectors since they're literally all fake unless you're pulling crusty injectors out of an RX-7 in a junkyard. ;)
Fuel Injectors - Miata Turbo FAQ

For reference I pulled mine out of an rx8 myself, they are 100% oem densos. It's not just the fakes that suck now. All of them are not worth it. If you try em you are straight rolling the dice if they are good or not.

Maybe the previous RX8 owner hat already replaced them with junk/fake injectors ? After all this has been going on for at least 6 years.

They are definitely oems, I've held fakes before and they are super light, like noticably lighter than oems are. I'd say almost 100% they are just in need of a rebuild at this point being, what, 19years old now?