Cold start tuning
 

Hi, I'm struggling to dial in my cold start, it's very cold here in MI today (5deg F) and i'm struggling to get my Miata started. I managed to get it to run after lots of messing around, but with clouds of unburnt fuel and AFR's around 8 ! once they get above 9 the car just stalls. Not sure if I have a funky O2 sensor or what might be happening, any help much appreciated. I've been plating with WUE and ASE, I know the curves are not smoothed yet above 40deg CLT.

So this is the longest I was able to get her to run, she cut out at the end. I did not turn the car off, seems to correspond to a significant and sudden jump in the AFR

MS3x
gt2554r Garrett
1.8

Thanks ! very much

I'll take a look at it. You around Metro Detroit?

That would be fantastic, yes, I'm in Royal Oak

OK, So I made a little progress, discovered my Fuel Pressure regulator vacuum hose was kinked. As the temps in Detroit came up to above freezing I was able to get the car started and running well. Now the temps are back around 20f and it will not start again. I just checked for spark - still can't get output test mode to work.... and I don't see any, making me think perhaps something related to temp is affecting spark output....any ideas ?

Update - I decided to experiment a little with the suspicion that something inside the MS3X box or cabin is cold and not working. I have a small space heater which i carefully put inside the car and let run for 20 mins or so. After the inside of the cabin was warmed up, I tried to start the car again and to my amazement I got a nice strong spark and was able to start the car pretty easily. Next step will be to diagnose why the car needs to be warmed up inside to be able to make it run.........

I would open up the Megasquirt and look for cold or broken solder joints. That’s a classic sign of a broken joint. When it’s cold the metal shrinks and there’s no contact; when it’s warm, the metal expands and contact is made.

Fantastic, thanks, that is what I will do. Anybody got any good tips or tricks on finding the bad joint, i'm assuming it will be warm when I get it all open....?

I found a bad solder joint on my board, just made a nice long inspection with glasses/magnifying glass and fixed it, but I could have gotten lucky... it was a hairline crack in the joint but definitely a loose connection

Take it out of the car so you can put it on a tabletop to inspect it with bright light and maginifcation. Use google to figure out the difference between good looking solder joints and bad looking joints. Then go joint by joint and inspect. It’s time consuming but not hard.