Megasquirt Idle PWM settings help

Hello, I have installed a Megasquirt 2 ECU, V3.0, with MS2Extra firmware, in a carburetted engine the engine operation settings are correct and it has had an excellent improvement in fuel efficiency as the carburetor has been replaced and ignition conventional by injection and electronic ignition.

Now I have a configuration error in the activation of the idle valve, when the vehicle runs downhill and I stop, the engine shuts down, I have tried to configure the injection cut in parallel, but I am unable to know which configuration can correct this error, this only happens downhill and apparently when the injection cut is activated as a whole, because when I drive flat or uphill it works normal, the engine does not turn off and works correctly.

I enclose the closed cycle PWM idle valve configuration, with the initial table, the engine idle speed (RPM) table with temperature and the main fuel map.

Can someone give me a hand?

Thank you...

Can't give you a definitive answer, but having dealt with trying to get this to work properly in an old Bug I converted to EFI using Microsquirt (same firmware) there are a few things I can think to check.

TunerStudio has a lot of "indicator lights" at the bottom, I'd suggest watching those as you re-create the situation. The two to watch in this case would be over-run fuel cut and closed-loop idle, make sure both of those are behaving as you expect - that can help you diagnose the problem. Try turning off over-run fuel cut and see if that fixes it, a very simple thing to try. If that fixes it I wouldn't suggest leaving it turned off but it could give you a point of where to start.

One thought, check to make sure your throttle is reliably closing. It has to see less than 1.5% throttle on the TPS, if it's hanging at 2% then the idle valve won't open and the engine will stall. You're describing that the engine does this after coasting down a hill, one possibility is if you're gently closing the throttle it doesn't close all the way, gets stuck at mostly closed (not enough air to idle the engine) but not registering "closed," while when snapping it shut it goes all the way to the limit screw. I might suggest monitoring the TPS in TunerStudio with the engine not running, crack the throttle then close it very gently and see what it does. That's a problem I'm dealing with right now on my build as a new throttle body breaks in. If that's part of the problem you could increase the throttle setting at which it activates idle.

A problem I struggled with for a while was running my closed-loop idle with "use previous value" starting point (instead of initial value table), the first starting point on start-up is with the idle valve max open. For some reason the idle valve my car is equipped with (the one used on later stock Mexican EFI Beetles) is huge relative to the needs of my engine and will gun the engine to like 3K RPM at full open. I had a lot of troubles with it not entering closed loop idle especially after a hot-start. The engine would rev up rapidly then cut out until RPM dropped, then rev up, cycle repeating and never finding a proper idle speed. Watching the aforementioned indicator lights I saw that it would reach fuel cut, given the closed throttle and RPM. To enter closed-loop idle and begin "seeking" the proper setting it would need to have a stabilized RPM, there are maximum RPM-dot settings for it to enable that and it obviously wasn't getting that, so the engine would keep surging like that. Figured out if I turned off fuel cut it would surge up, stabilize, then enter a proper closed-loop idle, now knowing this setting it would work properly for the rest of the drive. Found a kludged but effective solution to all this, I disabled over-run fuel cut then set a secondary VE table based on TPS (as "multiplicitive"), and set the bottom row above 1500 RPM to 0%. That way it cuts fuel above 1500 RPM and closed throttle, this acts effectively as an over-run fuel cut while also limiting idle RPM through leaning it out - can't run without fuel. (I know leaning can be dangerous but I figure it's not too bad at idle speed/load). Thus first idle it surges to that RPM, hits that lean-out, stabilizes, then enters closed-loop and works properly. Ideally I should tune it with initial values, but my engine struggles with that as the air-cooled coolant sensor will detect a much hotter engine if I shut down for 10 minutes then re-start, so if I drive a few minutes, park for 10 minutes, then drive again the CLT sensor detects fully warm engine when the engine isn't warmed up, if it went off an initial value (or open-loop) it would think the engine is warmed up and stall. Don't know if it would relate to your situation, but maybe this story could give you some hints in your troubleshooting process.