Stall when coming to stop with AC on
 

I've got a DIYPNP that has been working well for about 6 months. I've just installed the FM happy meal about 3 months ago and all was well. Until I started using the AC.
If I am sitting still, the AC idle up works and does not even begin to stall the car. However, if I'm driving, and then push the clutch in to prepare to stop, the RPMs drop enough to stall. Most of the time, it doesn't stall, but it has a few times. I'm guessing this is because of the lightweight flywheel in the happy meal.
Is anyone else having this problem? My research has turned up people that are having issues while sitting still.

do you have a 1.6?

Are you using a/c idle up code?

It is a 1.8. Forgot that may be important!

Yes sir, using idle up. When I get home, I can post the setup. When I'm sitting in my driveway, it idles fine and idles up like OEM (or at least how I remember it).
While driving, I can really feel it lose power when the compressor kicks on. If the compressor is on, and I'm driving normally then let off the gas and press the clutch in, the RPMs fall quickly and then almost stalls. If the compressor has cycled and is off, then this does not happen.

Post a log of this happening with compressor on, then not.

Ok, while trying to get the logs, I discovered that it will only try to stall after a hot start. I drove around this morning and could not get it to do it. I drove home from work - same thing, could not get it to mess up. I pulled over in my neighborhood, and turned the car off for a few seconds, and started in back up, and started a log. As soon as WUE ended, to started going. Record 220 is the throttle lift and clutch in. That was the first almost stall. I turned the AC off and performed another test. Record 680 ish was a second lift RPMs fell as normal and didn't attempt to stall. Is there an AC compressor is on switch that I can display in the Log Viewer?

Log is attached.

Edit: I did a ton more testing and found that I don't understand how the AC Idle Up actually functions because it says that the AC is on even when the compressor is not actually on. Either way, I found that once the car is warmed up and been driven a bit, I can turn the AC off, and then back on and that is when the problem starts. I tested it sitting still in my garage just now. I can make it almost stall and the car will turn the AC compressor off, wait a few seconds and then turn it back on again. This creates an almost stall loop until I give it some throttle and let the motor settle down. But it will repeat the next time the compressor cycles. It's like AC Idle Up is not functioning if I manually turn the AC off and on or turn the car off and on (hot start).

Is the AC indicator in TunerStudio supposed to be on even when the compressor is off? I will attach that log too.

Hey,

I need to understand how the idle needs to be tuned first, you can check my writeup.

Mega Miata: Closed Loop Idle REV 2.1

Thanks elior. I actually used you blog a lot when learning and getting started with the Megasquirt.

My car idles great without AC. And the car idles great with AC on too. When driving the car acts normally. But if I turn off the AC and turn back on later (either by the AC switch or blower speed, or turn the car off and starting it again) then it does not like to idle when the compressor cycles on.

I did some playing around with the idle settings and hopefully I've gotten it sorted. If so, I'll post the settings I'm using. Thank you for the suggestion!

This is the exact same thing my car is doing! Did you ever figure out the issue and get it solved? I’m running the mk kit with ms3 pnp and 640cc injectors. Any help woild
be appreciated.

Use closed loop idle
Use closed loop idle initial value table
Use A/C idle up

Change settings and see what happens over bumping old threads