I've been tuning the hell out of my Megasquirt lately, and I've got the car to run smooth as hell. I'm a happy camper! But there's still one small niggle to be solved.
I searched on this matter here, and on other forums, to no avail. I can't figure out why my car isn't fast idling. I've double and triple-checked all the configurations and nothing seems wrong.
These past few days I've been hand tuning the VE Table, and some other things. However, due to some unforeseen factor (could be the cold weather, or something I messed up while tuning) the car now idles very rougly right after startup. I had this happen the first times I started the Megasquirt, but then it was pretty normal so I didn't pay much attention to it. Now it is back. When I turn the car on, the engine starts then the idle oscilates heavily, and almost (or sometimes even) stalls. I need to put my foot on the accelerator, to keep the revs at 1xxx rpm for one or two seconds, and it stabilizes, but when it does, it goes around 950 RPM which I reckon is the slow idle.
Also, it only does it when cold. While hot, it starts and idles just as it should! And when cold, the idle works fine, only it slow idles. The stumbling and stalling is only on startup.
My fast idle is set for 1400 RPM, and since this is a '91 Miata, it has no fast idle valve, just the regular ol' PWM idle valve. Could it be a problem with that bypass valve on the side of the inlet manifold? Still, this doesn't explain why it doesn't fast idle. It must be a tuning issue.
Anyone that can shed a light on this matter, will be greatly appreciated!