ElZesto

Hey Miata turbo people. I come to you in my time of need with no idea what to do to fix this problem.

So around 3 months ago I upgraded from a ms2diypnp to a ms3x built by me, following the super helpful instructions on trubokitty.com and the assembly guide on megamanual.com. After getting it all built and building the patch cable from a diybob to the ms3/x ECU I slapped it in, loaded in a base map and started it. I did some initial tuning and test drive and it was smooth sailing but my time was super limited because I was preparing to move a few hundred miles so I didn't have time to get it dialed in, and I was going to trailer it anyway. Anyhow fast forward to the past few weeks and I got the car back to my new place. As soon as I got back with it and sat in it I couldn't resist going for a small drive. I warmed it up and went and drove it for maybe 20 minutes and came home and parked it in it's new garage. All was well. Next day I went to start the car and get going on doing some actual tuning because it's running crazy rich on the basemap, and that definitely needs to be fixed, but now the car will start, idle's fine and then if you rev it it will lean itself to stalling returning to idle.

I couldn't figure out what's wrong so I sent a data log to two of my buddy's, both of whom pointed out the voltage was being weird and one suggested to disconnect the alternator and see if that fixes it. Well hot dam it worked, and so I assumed that the alternator must somehow be toast but I had my doubt since it was still dying at a healthy ~14v, so I replaced it, and it still does the same thing with the alternator connected. I looked into if there was any sort of alternator control on the MS I needed to be using but the only thing I could find for miata's is for NB's and since its a 95 I don't think that's the solution, but id be happy to be wrong. I really have no idea what the problem is.

The other strange thing that it's started doing is when the key is turned from ACC to ON the first time, it primes normally, but if I let it fully prime, then turn it back to ACC it doesn't actually turn off the ECU. The ECU drops to 7.5v but it doesn't shut down. If I turn the key to ON and then back to ACC before the fuel pump finish's priming it will turn the ECU off normally. I was curious about this so I probed around the wiring to see what was feeding the ECU voltage and I found that the tps (pin 2m) was giving it ~7v. Idk if there's some filtering I need to add/enable to fix this, but I'm also skeptical this is a hardware issue in the car since this wasn't problem with the old ms2 diypnp that was in here before.

I've triple check my harness patch, and my ECU PDB and found no problems. If anyone more knowledgeable than me can point me in the right direction I's be stoked. Thanks homies.

Let me know if there's any other info I can provide to make this easier to diagnose. I appreciate your time.

Modifications to engine:
MS3x
GM IAT sensor for speed density
Deatschwerks DW200 255lph fuel pump
Radium Engineering high flow fuel rail
450cc RX8 yellow injectors (ebay bullshit - was actually going to be the first upgrade but I need to get the car actually again running first)
td04 turbo out of a wrx
Log Cast Iron manifold
3" Custom Exhaust
Innovate LC-2 Wideband Controller on Bosch LSU 4.9
Other bit's and doo-dads but nothing I think is relevant to this

TL;DR: Built MS3x and patch to harness to run it. Ran fine for first two test drives, but very rich and not tuned yet. Now will start and idle fine, but will lean and stall after revving. If I disconnect the alternator completely it runs perfectly normally. Replaced alternator, still doesn't work.

P.s. attached is my tune file, a data log of me keeping it alive with revving, a log of just revving it once and it stalling out, and a log with no alternator where it runs normally.

ElZesto

So I've solved this problem, and it of course was as stupid problem fixed with the always correct answer: tune it.

Basically I hadn't actually tuned my injector dead time/voltage% curve. I found this post: https://www.miataturbo.net/ecus-tuni...ad-time-56061/ and followed the instructions and its good to go now. Hopefully another dumbass will have this issue and this will help eventually.

I'm still very confused as to why it did run normal for a handful of short drives and then never worked properly until I fixed that part of the tune. I guess I'll toss it up to shitty ebay injectors being funky I got some legit ones on the way now since that's basically the only significant weak point in the car (aside from the fact I own it but that's really more of an overarching issue), and with this much time spent on it I don't really want to wait for them to **** the bed during a race.