Tuning Idle Valve MS2E Rev build
 

Hi all,

As per my other thread, I have installed the MS2 and got up and running, even went for a couple of quick Autotune's.

However, I have cold start and idling issues. Now, I think the cold start issues are linked to the idling issues so let's start there.

I have read THIS GUIDE from MX5Nutz start to finish, which is a bit pointless as my car fails at the first hurdle.

I select Idle Control > PWM Valve >Open Loop Warm Up. Start the car, it idles anywhere between 2k & 4k RPM

I go to - Test IAC - Steps =100 - Enable test, if it isn't already idling high it shoots up to 4000 RPM as per the guide. But then when I start to walk down, by the time I get to 97 it drops down to idle between 1000 and 2000! WTF!? Therefore I can't find my values to plug in to the next settings table.

If I click 'stop testing' it shoots back up again. If I click 'enable test' sometimes it shoots up, sometimes it dies down to 1000 or so.

I have tried inverting the valve settings I have tried copying numbers of the internet but nada. Nothing seems to work.

It's annoying as 1) I have to manually idle the car with the gas pedal from cold start and 2) once it is warm it idles fine and can be taken for a drive.

There must be something obvious I'm missing here.

Any help would be greatly appreciated.

Thanks!!!

P.S.

I have searched and searched and searched and read up on ASE & WUE but I don't think I'm even getting that far...

If I hit the gas pedal as I am cranking it (as I do in most cars anyway) it starts within a second or so. The issue then is, I have to keep my foot on the pedal to keep it idling, if I lift my foot it drops to about 500RPM and stalls itself out running mega rich.

In an attempt to resolve the issue I 'tweaked' the ASE & WUE that much that my WB was showing AFR's in the 10's and the car stunk of fuel and was miss-firing, shaking like a sh****g dog and still cutting out when I lift of the throttle. I reverted back to some Braineack settings I found during research.

The idle valve settings are nearly never that high. You are well past the non-linear operation of the idle valve, so it's not surprising that it doesn't react linearly.

Go run the valve, all the way from zero to 100.

I've tried the test at 20 & 30 steps and it either doesn't do anything, or shoots back up to 4k. :-s

I was trying to follow the guide.

Is PWM the right setting? Or am I using it wrong.

Do you have to reduce the amount of steps and then enable test mode every time you change the value?

Do you have any settings I can try and copy and go from there?

Thanks

If you have a NA, the idle valve frequency should be 158 or 183 something, as close as you can get to 170hz. If it's an NB, you want 480hz.

NA idle valve when idle bleed screw is set proper is somewhere inside 18-38 or thereabouts.

NB, I have no idea. I hear it's around 60-80% or around there.

Apologies, I have a stock 98 NB 1.8s.

I tried turning the frequency up to 372Hz or 412Hz (can't remember which) and it revved even higher.

Here are my current settings, when PWM Warmup is used:-

https://www.miataturbo.net/attachmen...ine=1454883619

https://www.miataturbo.net/attachmen...ine=1454883619

Set the frequency to 480hz, then go to idle valve test mode and sweep 100-0.

All the way, till it stalls. If it revs higher than 2K, that idle duty value is useless for closed loop control. Why would you ever need to idle at 2K? Does that make sense?

I can't explain any clearer than this. If you aren't even going to do what I ask I can't help.

I will certainly go and try that and I thank you for your help so far in replying, unfortunately it's 22:30 here in the UK so I can't try it right now without having the neighbours wanting to kill me.

To clarify, in the test window. Do you have to enter a value and click enable test and then change the numbers.

OR

Do you have to enter a value, enable test, stop test, change the value, enable test and so on?

It's erratic behaviour earlier has me doubting that I used it correctly.

Enable test mode, then cycle up and down through idle duty values. All you have to do.

Thanks, I'll get on that and report back.. Unfortunately it's looking like Wednesday night before I can work on the car again. But then I will be using it for 4 days as my daily so hopefully lots of time to tune.

Thanks

Wilson

Hi,

A thought occurred to me ahead of getting time with the car tomorrow and just want to check I am right.

I assume I should start her up (with Idle control disabled) get her warm by manually holding the throttle to achieve an idle, until warm where it idles on its own. Then turn off, enable PWM Open Loop (Warm Up), power cycle and start back up to do the tests?

I don't want to have it revving up to 4k for a prolonged period when stone cold.

Thanks

Yes, that should work.

So, I took your advice and tried again. I fired her up, modulated the throttle manually until it was warm enough to idle on it's own and drove her to a nearby truck stop / lay-by.

Set-up the idle control valve to enter test mode and away we go. What I actually did, to stop it revving straight up to 4k was to set the steps to 50, thinking this would give me a half way ground. Well it did and idled at about 2000. Strangely, as I was increasing the value the revs were getting lower I got up to 83 Steps and it was idling at 1096 RPM...The lower the number the higher the revs.
:idea:
Turn 'invert' on in the settings!
Did that, ran the test again, now at 60 Steps it's at 4k RPM & at 18 it's at 1059RPM.

Finally!

Plugged the numbers into Open Loop and bought her back down to my weekday accommodation meaning a solid hour and half of auto-tune goodness.

I have no idea why it was acting so oddly when I tried very similar at the weekend, other than me panicking 'cus it was revving so high and turning it off and not having it set to 480Hz.

I'll follow the rest of the Nutz guide and set-up closed loop after I have finished tweaking the fuel table for N/A Stock.

Thanks for your help!