For the love of God, help me get my A/C to stop stalling my car!
 

Title says it all. Getting hot as balls in southern Louisiana.

I have a 91 with a first-gen MSPNP setup. Running a bmw variable tps. All other details in my sig.

If I attempt to run my a/c the car idles super low (like 300 rpm low) and will stall when coming to a stop if it's running.

Other than that (and a problem with IAT heatsoak), the car runs pretty good.

Oh, and I am an old-schooler that hasn't been around for a while, so I'm....ummm.......still running MegaTune. :m-freak:

So what do I need to adjust to get the car to stop stalling? Is it a TPS specific setting?

I'm like that cat that isn't good with computer.

MS1? Live with it or upgrade to an MS2/MS3.

There is no living with it. It was 90 degrees today and it's just mid-May. Ironically, the car didn't start doing this badly until AFTER I installed the TPS.

I made my MS1 work with the A/C without stalling. I screwed around with the idle and dashpot settings until it doesn't die anymore.

Here is where I ended up. You may need to play with it to make it hard work for you.

Attachment 185418

Re-purposing the EVAP solenoid to a regulated vacuum leak when the A/C in on is another popular band-aid fix for MS1 users that need A/C.

There are many old threads about this problem and bandaid solutions on ms1. I tried to tune the a/c on idle droop out to no avail with ms1 before upgrading to ms2. You can only mask the problem by using a very high warm idle so the a/c activation combined with other electrical loads only droops the idle to ~850 with some "acceptable" oscillation.

Upgrade to a ms2/ms3 or a reverant ms and you will have a/c with a smooth idle.

ms2 a/c idle options on different firmwares:
msextra
https://www.miataturbo.net/attachmen...ine=1369176660

gslender alpha code
https://www.miataturbo.net/attachmen...ine=1369176660

which msextra firmware brings in the A/C Idleup menu? I can't find it in my Standard 'release' status 3.2.4.

Dave

Try the latest 3.3 beta 13.

Ok cheers, I'll give it a try.

Ok so like my southern brothers from other mothers Im miserable without AC and I have had zero luck controlling the load of the AC compressor with the PID code in my DIYPNP. I cant for the life of me figure it out. Ive gotten it to almost work but coming to a stop, clutch in, and the damn thing stalls. So I have been reduced to turning off the clutch while coming to a stop or holding the idle up manually. This sucks donkey dick until I hit the highway, DUH! So anyhow, I stumble across this thread and see that beta 3.3 13 has AC idle up function. Fantastic I thought! Burned it and now I don't know how to make it work. I was thinking that this was some magic bullet fix but upon further review something tells me I need to jumper something in order to make it work. The trigger options are FLEX, PE1, PAO. I am using PAO for engine fan control as my DIY documentation suggested, but isn't that an output? I tried that since when AC is on that fan is also on and therefore should trigger the code, no? Not only did it not idle up but it caused a Megasquirt conflict error. I would think its looking for an input? I would like to use FLEX in the future so I guess that leaves me PE1. So after reading all this babble, would I jumper my AC request from the AC switch to PE1? I don't wanna let the smoke out of my DIYPNP as it may be difficult to get back in so any insight is appreciated.

Side note: The car originally ran well with the 95 engine and AC but it quit working and I really wasn't in need of AC when it did. Between then and now I swapped to a 01vvt engine. Then came the heat and I replaced the clutch coil which had a damaged cut wire. Replaced it with a junkyard sourced coil and the AC blew cold again. This is when the impossible task of AC idle control came. Coincidence?

wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text wall of text thats not how it works. Learn how to tune, learn how your DIYPNP functions, and maybe you can get a/c idle up to work. Not that you even need it, since the PID code is suffecient enough to prevent a/c from stalling or running poorly.

It can be an input or an output - but it can't be a fan output and an A/C input at the same time. That would cause a conflict error.

Run it through the Input 1 or Input 2 circuit and then on to PE1.

Matt thanks very much for the help. As it turns out I almost let the smoke out of the DIYPNP anyway. So if any of you out there that are as retarded as me, dont try to share the out of input 1 to PE1 if it is already going to your ac clutch and fan relay as it will cause all sorts of issues, even fueling to be way off. Thats how mine is according to the documentation and it works great for controlling ac/fan function but to get ac idle up to work properly you have to use an input exclusively, like I did with input 2. Once wired up right it worked great.

And Brain, I was trying to give as much info as possible so sorry that it came out as a wall of text. And I am trying to learn how to tune, and learn how the DIYPNP works, and how the PID code works. I have read countless threads on peoples issues with idle and ac so I cant be the only one trying to learn here. I even read that crazy long thread where one forum member suggested the reason it doesnt work for most is that the P/I/D should be more like P/D/I as he says the code is wrong or something such. Ive done the best I can with fueling and spark, and even cleaned out the valve to take out mechanical error. Anyhow, thank you for your suggestion and I did try to find more to it than "I need to have ac idle up function". As it turns out I had decel fuel c/o set all the way down to 1500rpm. That was definitely causing the stalling when clutch in.

However, I have seen screenshots of your idle with turning ac on and off and I cannot get close to the same results, even with ac idle up. For whatever reason the code does not open the valve up when a load is sensed. I will keep messing with it but for now it doesnt stall with the ac and that is a huge improvement.

aim for greatness:

A real MS1 solution is posted here (this is a real fix -- AC idle-up software mod):

https://www.miataturbo.net/megasquir...de-hack-73751/

However, you need to know your way around software to implement this. So, choices are:
1. You are a software guy and can implement the described MS1 AC idle-up hack.
2. You know a software guy that can implement the described MS1 AC idle-up hack for you.
3. Live with sucky MS1 AC idle droop and apply band-aids as best you can.
4. Upgrade to MS2 or 3 that has AC idle-up code built in.

Pull the ac.. works wonders.

OP is in Louisiana. I'm in N. TX. Pulling the AC is not an option.

my a/c only works on fan speed 1. I thought to myself today in 95° weather, there's no way i'm ever getting a car without an a/c again.

Yeah, the heat and humidity in N. VA. can be pretty oppressive. I can clearly remember marching around the parade grounds in Annapolis with a lead-filled M1 Garand + Bayonet in that heat. If you didn't keep your knees bent, you were guaranteed to go down. Going down with a fixed bayonet was always interesting to those around you.