MS2 PNP Issue with Idle Hang (NA8)
 

Hi all, New to the forums so be gentle lol. Still learning the search function(s) of the site and browsing forums.

I'm having some issues with my MS2. Its installed in a N\A 97' Miata that has had nothing done to it other than purple NB injectors from the previous owner and I installed a Q-Max coolant rerout and dual row radiator as I'm planning on installing a rotrex I got last year. Wanted to get the things such as suspension, wheels\tires, clutch, tune, etc. done before I install it. Thought I would take my time and learn things as I go as I'm in no rush to get it done.

One big issue I can't find or figure out for the life of me is this idle hang I'm having. Once warmed up and cruising around. If I come to a stop at a light or otherwise. My idle will hang anywhere from 1200-1500. Sometimes it will slowly climb up to 1500 before CL Idle kicks in and brings it down. I've played with what I could find and understand searching the forums. But with my limited knowledge of tunerstudio and MS2, I'm not having much luck.

My other two issues, (Hot and Cold starts), are slowly being worked on as I learn from reading countless threads.

Thanks in advance!

https://cimg3.ibsrv.net/gimg/www.mia...89802c5649.gif

that would help huh lol. Here it is. just did the log today.

It is your closed-loop idle initial values.
https://cimg0.ibsrv.net/gimg/www.mia...dbaa6bf5ce.pnghttps://cimg2.ibsrv.net/gimg/www.mia...c825c7178a.png
Look at how when the car is idling around 1300 rpm the idle valve is open 38%. Then when closed loop idle kicks and targets 900rpm (I believe that is what you have it set to) the idle valve closes a little and is now about 31%. This means that at 900 rpm and a MAT of about 70-75 degrees your car requires 31% Idle valve duty.

Now looking at your closed loop idle initial values table at 900 rpm and 70 degrees you have an idle valve duty of about 37.5% add 1.02% for your dashpot adder and we get about 38%. So it makes sense that the car had the idle valve open 38% before closed loop idle started. Tuning your initial values table will fix this, you might have to change the dashpot adder as well but for now just try to figure how much idle valve is needed for each idle rpm and manifold air temp.

Another tip I can give you is that you will need more idle valve at hotter temperatures. Hotter air is less dense, which means less oxygen, which means we need more volumetric airflow to compensate.

I went ahead and redid your initial values table, give that a try.

What he said ↑↑↑

also you have CL Idle PID activation settings: TPS<3% and load>22% and delay 2s
I would say typical setting is TPS<0.5% and load>26% and delay 1sec

Change overrun settings accordingly (below 0.5% and below 26%)
Your EGO PID values 2/20/2 look unusual too.

Thanks guys. I'll give your advice a shot and see what it does. On PID Delay(s) I'm unable to make it any lower than 2 from what tunerstudio is telling me.

https://cimg6.ibsrv.net/gimg/www.mia...1728047c43.jpg

Upgrade to a ms3+ or leave it at 2 ;)

And if you have a MS3 on non-beta, leave it at three because there's some bullshit bug for the last 3 fucking years.

Megasquirt Support Forum (MSEXTRA) ? possible afterstart pwm idle bug in 1.5.1 (View topic)

Thanks all for the assistance, I greatly appreciate it and learning more on how to dial things in to the sweet spot.

I can see why I would want to upgrading to a ms3. But we have a guy here in Ohio that gave me a killer deal for a hand built pnp ms2 with great support. Only issue is I believe they are limited in the tuning aspect of it all. Thus I reached out to the rest of the world for assistance.

*update*

The new initial values go and changing the pid activation settings. Its worlds better already, the idle comes down on its own to around 1000 before CL idle kicks in and takes it to 900. After this is sorted, I'm going to need to look into how to stabilize the idle better when under load. I have A\C and still and found if I turn the blower on HI and the headlights on. The idle will drop as low as 400 and seamingly struggle to get to 900. Would it be possible to steer me in the right direction on that one?

I also found that after a drive yesterday. It was 70 out and I had to richen my idle a little bit. It was holding around 15-15.5 afr before ego kicked on. Did the same thing today as well and its around 50 at the moment. Now the idle is nice and smooth. I forgot to change the overrun settings so I'm going to do that and take it for a spin again today and see how it goes.

Ill have a good log for you guys to take a look at if you're board. I'm working on learning how to read the logs to see what I'm actually looking at in conjuction with how the car feels.

What is your voltage doing during the idle droop? You may be trying to tune out a bad alternator if it can't handle full blower and AC at the same time.

From what I'm seeing. At cold start it's 12v. During warmup it's 14.1v-14.2v. once warmed up it holds at 14v. When I kick the lights and blower on full. It'll drop to 13.9v for a split second then go back to 14v like nothing happened. That's today though when it's 67-ish in the garage.

The log I have is one I made on April 5th. I apologise in not getting back sooner.