E420c start/idle issues
 

I have had this ECU installed in my 2000 Turbo Miata for a few years now. Despite my best efforts, there have been a few issues that i have simply not been able to resolve. The most annoying of which is getting the car to start. I have had carbureted vehicles that i have had more luck with getting consistent starts out of.

I have tried different settings with and without the idle air control valve being used. I am able to get better consistency without, but it is still not perfect.

Basically, when cold, i can get the car to start rev up and then die within 1 second. I usually have to use some amount of throttle to get it to stay running but even with that it still takes multiple tries.

Please help me figure out how the hell i should go about fixing this.

Below you will find the current .ecu file, a datalog and youtube video for a cold start, and also a datalog and youtube video from a warm start.


Thanks all,
~Jared~

Alright few things, are you set to control the idle valve with the adaptronic ecu or the stock ecu?

I see few problems with ur ecu i'm going over it now. No worries we'll figure this thing out.

Is this on stock coils? If yes change the dwell to 4500. Looks like your spark is blowing out while its cold and then it idles.

Bump the minimum idle to 100. (just while you're experimenting with trying to start it)

In the corrections tab
Increase the timing of the enrichments to 20% - 10000 and 10% - 30000
lower the cranking timing to 0

At last you're adding way too much fuel. You might want to reduce it a bit.

I got a little bit of help from Andy on the Adaptronic forum. Apparently there were some major errors (ridiculous values) with the correction tables and a few other tables. The car had been sitting for a little while and i am guessing that happened since the battery went completely dead during this time.

Anyways, things are working much better now. The post crank idle settings were a little high, but i was able to tone that down easily enough.

I've also adjusted the high load coolant enrichment table so that it has a bit more fuel at high load when cold.It does drive much smoother now with the extra bump to the high load coolant enrichment. i never expected values that rich to actually run well, but i guess they work on a cold engine.

That being said, here are the results of where i am currently at:
This car is on stock 2000 coils. I did destroy a set once by having the dwell set too high. Are you sure that 4200 is a safe range for these coils to be in?

Now that it does start just fine, i need to focus on getting a good idle in both low and high temp conditions. I want to keep this low temp post crank idle dip away, but i don't exactly want a 2000rpm idle in these conditions. It seems to me that 1 step to the PWM is enough to create a large(200-300rpm) difference. What frequency is your IAC valve PWM running at? Mine is at 500Hz and i was wondering if i could get a little more set point resolution with a different frequency.

cheers,
Jared

Our year coils are suppose to run at just under 5k, i've have ran mine at 4500 since I installed the adaptronic almost 2 years ago so far no problem. The NBb coils are the ones that are ran at 2500.

My iac valve was ran at 1k however now I have it set so stock ecu controls it. It's lovely. Idles at 1400-1500 rpm when cold then switches to 850-900 on hot idle and it's quite rock solid. One of those days I might switch back to adaptronic to idle to try to whack my head at it for a bit however i'm pleased with the stock ecu idle.

Extend/bump the post crank conditions a tiny bit. The problem I originally had was similar to yours, Cranks and then 2 seconds after the enrichments end it falls on its face, the cure was to extend the enrichment time few seconds more and give it time to stabilize from the start before they taper off.

out of curiosity, how did you go about setting things up so that the stock ECU maintains control of the idle air control valve?

https://www.miataturbo.net/adaptroni...install-60355/

Check out my pics, i'm assuming you have the board too. The other thing u gotta change is your settings for aux 1. Check my file on the 2nd page.

sweet! i will try playing with that

It looks like my board is a different version from yours.
Attachment 68337

Are you familiar with how to get the OEM ECU to control the idle functions with this style board?

I have the old board too, here's a How To Tune Idle link How to tune idle

I used this link to tune my idle. Good luck

That i do not know, you will need to ask Andy but my guess would be you'd need to rewire few things, add a resistor/diode somewhere and change few outputs. One for the temp for the coolant gauge to go from cold to hot idle and then to change the output so the stock ecu controls the idle valve.