John_B

I need help identifying an issue I cannot seem to resolve. Any information would be greatly appreciated!
First off , I have a 1991 1.6 Miata that ran fine on stock ecu/bonestock mechanically. Since then,I have put in MS2, 640cc flowforce injectors, GM IAT air temp sensor and AEM X-series wideband. I followed all instructions per DIYautotunes website and made sure the MAP line was not kinked. I have gotten the car to idle, but within 10 seconds or less goes from 13-14AFR to 21AFR, then eventually it dies and shuts off. Because I don't know what I'm doing in the tuning aspect, I had a real tuner come try and fix this issue yet no matter what he did the car would go lean and die out eventually. I replaced all exhaust gaskets near the wideband and ensured there were no leaks. I checked the spark plugs and they had fuel on them. It seems as if MS is giving the fuel to the engine but the sensor is not capturing it. Once gaskets were replaced, the car would still go lean! I'm starting to think its a bad wideband sensor but I'm not entirely sure because I took out the sensor and sprayed some butane on the tip of it and the gauge read very rich. To clarify, the car will idle for about 8-10 seconds then go lean. I wired the signal wire and ground wire directly to the ECU's option port for accurate readings in TS. The GM sensor is working, the Wideband gauge is reading, the MAP sensor is working and the fuel pump is brand new. What do you guys think the issue is ? thanks in advance, this is definitely one of the more frustrating problems in my journey to boost this damn car!

rwyatt365

Attach your tune.

John_B

Okay so when completely cold, it'll start for a good amount of time and idle, then just die out of no where. I attached the tune , along with the two datalogs: "start for MT" is from it being cold until it dies, "start after warm" is the car starting again after it died.

HowPrayGame

EGO does nothing during both of those logs, I don't believe its related to your AFR Gauge, I assume that is telling the truth.

When the car cold starts, its at 110 CLT Temp, when it stalls, its at 132ish and the car stalls when it reaches 135 clt.
This looks like a fueling issue caused by your WUE table being used as a substitute for adequate fueling when the car is not warming up. Looking at your WUE table that guess appears to be correct, will require changing your WUE back to a basemap table and bumping your idle VE cells up a ton so the car doesn't stall when it warms up due to a poorly tuned VE table/WUE table.
Your Req Fuel Injector CC is labeled as 600 instead of 640cc, change it to 640cc at the very least and recalculate your req fuel as this will also throw off fueling.

WUE Table below for reference. Crossover point for 128-158 is where the issue happens, this is also where the car stalls from lack of fuel. When I installed FF 640CC injectors on a 1.6, I had to bump up the VE table from the base map A **** LOAD. Do this until the car doesn't stall from lack of fuel.



Almost all cells are maxed out, a sane WUE table would look like this

John_B

thank you for your help, im not too familiar with tuning however youre saying i should put the WUE table back to basemap and bump up the VE table dramatically ?? im already like at 100 in the idling cells, how much is a "**** LOAD" ?? i have it at 600cc because i read that miatas have a fuel pressure at around 32-38 psi, so i plugged that into the flowforce website calculator and it gave me 600cc/min. Thats why i put 600cc instead of 640cc but im not to sure

HowPrayGame

Correct, tune the VE table first then (after reverting the WUE table) make small adjustments to the WUE table for additional fuel while the engine is cold. The final row should remain at 100 so you aren't permanently pulling or adding fuel across the entire VE table .

I had to change the VE idle values up about 80% or something insane like that, try adding 10% and keep bumping it up in the idle region til the car idles and doesn't stall out due to lack of fuel. The AFR gauge isn't lying at all, add fuel til the car is around the 13-14 AFR area when warming up. The change in fueling on the WUE table tapers from adding 63% to the VE value to adding 0%, and it stalls about halfway in between. Increasing idle VE by 30% and going from there will probably do the trick.

NA's have a 43.5 PSI fuel system, multiplication of the CC's is only for NBs according to Flow Force's calculator as they have a 60 PSI system. Your injector deadtime settings seem correct.

You will need to idle rich if you plan to keep the fuel injection untimed, which you may be limited to by the ms2 without additional wiring, not sure, I am unfamiliar with a MS2s featureset.

Left0verCurry

That AFR target table also looks so weird, are you sure this was done by a "real" tuner? I really hope you didn't pay that guy.
Also that VE table looks way too high already, for reference my 550cc EV14s are around 55 at idle.
Start by reverting the WUE to the table posted above by HowPrayGame.
Data log it and see if it stalls, if it doesn't then adjust your VE tables to idle around 13.5-14.7 for now.
Then test and adjust your idle valve so you could switch from open loop to closed. (Where)


Edit: Try this tune file, i adjusted the injector size, WUE, AFR table, and a couple other minor things. I didn't adjust the VE table, you'll have to do that and i'd recommend starting the idle cells (25-45kPa) to around 65 and move them around till you idle around 13.5-14.7 AFR.

John_B

here is a data log of me cranking it with your tune on it , it wont start but possibly the battery is low?

John_B

here is another crank with your tune, and my battery jumped almost wanted to start

Left0verCurry

Try this one, i switched the VE table from yours to base map's. Also where are you located?

John_B

Thank you , im located in El Paso TX, let me try the tune

John_B

gave it a little more fuel while trying it and it almost started

Left0verCurry

That explains your coolant temps being 100+.
Try bumping the idle cells of the VE table by 5 or 10 and see if it helps.
Also, does it start in closed loop?

John_B

So it turns out the Megasquirts ECU fuel pump relay was bad, which is what caused the car not to idle and go lean, just incase anyone had the same issue.

Luckde

So John, just for a point of clarity, you had to send you ECU in for repair, or was it an external relay.