Inconsistent idle
 

To start, a few details about the setup...
2001 NB with VVT
Rev MS3X
LC-1 wideband


So I just got my MS3 set up and running yesterday. All is going smooth now with the exception of it sometimes idling rather high (2000 - 2100rpm), and usually when it does it, the motor will rev up and then drop RPMs as if it had lopey cams.

It doesn't do it all the time, and haven't been able to connect it with anything specific as to when it decides to do this. Whenever it happens, I can turn the car off, let it sit for 5 seconds, start it again and then usually it idles correctly (around 1Krpm).

Any ideas? :hustler:

Reduce your cranking PWM idle duty values or your idle bypass screw.

This happened to me after I pulled 3 degrees of timing because I had 87 in the tank. When I went back to 93 I added them back and got the oscillating idle. I pulled the timing in the 1800-2200 cells and it went away. It may not gave been the best way to fix it but it worked.

So I've been messing with this for a few days now, and I cannot get it figured out. I have realized that I'm running into an even bigger problem though....
It seems as though the MS is switching between tunes, even though I haven't set it up to do so. If I have it hooked up to a laptop with tunerstudio running, it runs great every time. Then if I disconnect the laptop and start it up, it seems as if it sometimes runs exactly like when the laptop is connected (with the exception of a higher idle rpm), and sometimes it will run really lean (but always idles at the correct rpm when it does this).

I know that you can hook up a switch to have the MS switch between different tunes, but I haven't done that, so I don't think that's the problem. Any ideas?

Update: I was able to replicate the problem while I had the laptop hooked up and TunerStudio running. All I did was shut the car off then start it back up, and all of a sudden I was running super lean.

I'll have to test out this theory a little more to confirm it, but I think it may be a difference between cold and warm starting the car.

Another update: I now can't seem to get it to idle correctly at all, no matter how many times I try restarting it.
At the same time, it doesn't seem to be running lean anymore... if I could fix this idle problem it should be running perfectly.

Where is your MS3 mounted? I am having a similar issue with mine and it seems to be changing when ever I move the MS3 around when I plug or unplug the USB cable. I think I might be pinching the vacuum line when I move it around. I'm also going to try the things REV said to do next time it does this to rule that out.

It's mounted in the same spot as the stock ECU. I thought it may have been the vacuum line as well, but I've been watching it closely and I don't think it's pinched or folded over or anything.

What'd Rev say to do?

That's where mine is "mounted" too. Somebody would make a killing if they were to develop a mounting system for this thing in the stock location.

Rev's reply is post #2 in this thread.

Alright, after messing around with trying out idle settings other than closed loop, then reverting back to closed loop and messing with the settings there and adjusting the idle VE table, I THINK I've got it running consistently good. If anyone would like, I will post a screenshot of the settings to show what all I changed.

Took about half an hour of me almost ripping my hair out to realize that there was a separate fuel map for the idle, and couldn't figure out why adding more fuel to the cells it was idling in wasn't changing anything...


One thing I tried to mess with and couldn't quite figure out is; in the settings for the closed loop idle control, you can set it to run off of an 'initial table value'. I tried messing with the table, but it didn't seem to change anything at all. Couldn't really find much about it by searching around on Google... does anyone have any info on it/use it? Would it be a better route to go than the default ''use last value" setting?

I'm definitely interested in screen shots in case I still have similar issues. I fired it up this morning and it idled fine. Drove it around in auto tune mode and the car ran great. It goes to the dyno next Monday to get really dialed in. It is a load cell dyno so he will be able to hit almost all the cells in the VE table and get it good to go.

Here ya go. First up is the Closed-Loop settings:
https://www.miataturbo.net/attachmen...ine=1381017805

And here's the idle fuel table I ended up with (your will probably differ, but you can use it as a reference if you want.):
https://www.miataturbo.net/attachmen...ine=1381017805