MS3X-1.6 Sync loss @ 4K, high idle
 

Hello guys, I've been having some trouble with the MS. It has a high idle, starts around 1500 and works it's way up to ~2200 as the car warms up (16-17 AFR), which I have no idea why. And recently, on startup, it will start then a few seconds later die down unless I turn autotune on, which then it will idle. Also, the idle with jump up and down if I don't have overrun fuel cut off.

Lastly, it is experiencing sync loss at ~4K rpm, I'm pretty sure my pots are set up right. You can see my build thread here https://www.miataturbo.net/megasquir...y-build-62983/

Thanks for your time. I have attached my current tune and a couple datalogs. Please let me know if you need anything else that I can help with. I will not be able to work on the car until this weekend so I am trying to set up a game plan for when I go home for the weekend.

Is your idle control on the MS3X?

you're not using the correct output; you have "FIDLE" selected, not "Idle".

Fidle is the the output on the Mainboard... I dont suspect you built the pwm idle control circuit on the mainboard when the same is built intpo the expander card.

Switch that.

Otherwise the settings look okay...but the PID probably needs a little help.

Never autotune idle. I say that, but you can't anyways--it's filtered out when CL idle is active--PLUS you're using the VE idle table in which the autotune won't tune. If you need to fix your AFRs at idle, tune your Idle VE Table by hand.




For the sync loss issue: Composite log the event, find out what sensor is dropping out, then readjust the pot a bit (going more clockwise) until it doesn't drop out.

Thank you sir! I switched it from FIDLE to Idle, also I'm not sure what PID is. As far as the sync loss, I turn R56 more clockwise, correct? and leave the other one be.
Referring to this

So I went home today, switched the fidle to idle, and it literally took a half our to get the car to start. It would crank and crank and crank and shutter and puff. It started a few times but then died after a few seconds. But eventually it did start and idle normally, still high at 2k and I have not the first clue on how to adjust it down other than the screw on the TB.

I did a composite log of the sync loss but I have no idea what i'm looking at so I'll attach it for anyone to look at. I'll also attach my crank data log to see if there is anything funky.

Welp, I figured out a couple problems. The high Idle was due to it constantly pulling air through the IACV. Which I block both ends and the idle dropped down to normal. Thumbsup.

I also figured out why it was having such trouble in cold starts. My temp gauge in tunerstudio is stuck at like 180 iirc. The dash gauge is working. This makes me believe when I did my headgasket, the plug didn't seat right. Though, i can't get my hand behind to the plug to check it. Is there an easier way?

Now on the sync loss, this is probably completely wrong, but, can I literally turn the pot while the car is on and revving until it quit losing sync? Or what is the better way to do it?

Fixed the temperature problem. But I still need help with the sync loss. It is code 38 (4g63) and I found this thread https://www.miataturbo.net/megasquir...38-4g63-69396/
so do I need the opto circuit?

vr crank and expander cam right?

most likely pot adjustment issue.

I'm not sure how to tell to be honest. I attached a screenshot of the log. Let me know if I need to upload anything else.

Can you tell anything? I would loooove to get this fixed. And my cold idle.

Did you set the pots with a multimeter?

Yes sir

I would verify your grounds. This sounds similar to a problem I had where I hadn't paid attention to the grounds on my ms3x. Car ran fine but would lose sync at higher rpm.

composite log the events and see what signal is dropping out.

I have two separate ground wires going out to the fuel rail. What did you have to do?

That might not be the problem, but it's certainly a problem. The fuel rail isn't exactly a great ground. In fact, how exactly did you attach a ring terminal to the rail?
Anyway, you want to go to the head or block. Possibly the intake manifold. The key is very solid contact and clean surfaces.

Further, the MS3 + MS3X harness contains 10 ground wires. Not all are necessary, but why connect only 2 of 10?

Fix your grounds. ;)

I mean inside the case. You may have a loose ground or you are missing one on the ms3x.

With a ground problem you wil have errors build up so it will work at low rpm.

Whaaa I coulda swore I read somewhere that that is the place to ground it! :vash: My wideband is grounded there as well. On which part of the head/block exactly do you recommend grounding then? I grounded the wires already in the stock miata harness, and threw two extra ones out there, if that's what you mean. I can't remember how many are in the stock harness right now. If this is the actual problem, I will be so happy. :rofl:

do you have any grounds coming out of the expander board itself?

Yes. This be my harness for the expander. Only pic I could find
https://www.miataturbo.net/attachmen...ine=1358220508

that's the mainboard harness. what about the expander?