Fluctuating Idle and Decel Problems
 

I just got my MS3X for my 99' two days ago and I've started tuning it. So far it's been going ok other than a few issues (stock ECU did none of this btw).

1. Cranking

The car takes like 4-5 tries to crank. I need to give it at least 60% throttle and 2/3 times it doesnt work. I can hear it firing and trying to start, but the most common issue is when i hear a event happen and then the starter just stops cranking and I hear it slow to a stop. I think this is called starter kickback I'm not sure. I adjusted my cranking advance (to 7deg) and it helped, but now 1/2 times it backfires incredibly loud out of the intake or the exhaust (either one). Which is bad for my neighbors.

2. Idle. The idle was not smooth when I got it out of the box, I found out the duties of my IAC (32 was the low which seemed high) and plugged them in and messed around in the closed loop settings until the rpm stayed relatively constant. It was still stupidly high, like 1300 rpm, even though it was set to 850rpm in every single menu. But overall stable, except for the AFRs. Which fluctuated from 12 to 16.7 every second or so. So I smoothed out the map (so that all the tiles in the idle portion are identical in both the main fuel map and Idle VE. Still fluctuates between 13.2 and 15.2

The second idle issue I have is when i come to a stop after moving (worse after hard braking/stop) the idle starts to oscillate and revs from 1100 to 2100 and drops sharply, revs up and drops sharply, etc... It doesn't stop until i accelerate again (which makes stoplights awkward for everyone around me, my exhaust is loud.) If I come to a stop and let decel and fuel cut happen and just coast to a stop, It never oscillates like this, just stays at 1300rpm.

https://cimg8.ibsrv.net/gimg/www.mia...771adc5523.pngIdle control fluctuation


3. Decel

When I decel, the afrs go full rich for a split second, then go full lean. At low RPMs it "rides the idle" way to high. I.E. I'm in 2nd gear 2500rpm and if I let off the throttle it's like I didn't do anything, the car keeps maintaining speed, and then for a split second sometimes it will go into decel and start slowing down and then the idle will catch it and bring it back up. This is stupid annoying as it means i have to downshift into first to slow down more without the brakes. Which i hate, I usually engine brake all the way down to 900rpm in 2nd and then clutch in and brake..


I attached my tune. My log was too big to attach.

I had a similar issue with the idle and afr, you can try bringing your "over run fuel cut MAP lower than" setting down a bit, 22 worked well for me. as far as cranking, if you're hitting 70% tps you will be in flood clear and that may be a sign that your fueling too rich on start up... your cranking pulse % is about 50-100 points higher than mine. I'm still learning and in early tuning stages myself but maybe that'll help?

I thought about the fuel cut, but the issues is that my car never reaches 22kpa on decel, its close to like 24, 25kpa. The issue I'm having is that it won't go into decel, not that it goes into decel too early. The higher kpa readings than everyone else online points me to vaccum leak, I just don't know where to look, or how to test it.

We need logs of the problems to be able to properly help.

22 is just where I have it, I could probably go up but from my understand it affects when you're idling. if you hit that value, at least for my instance, it causes my idle to fluctuate and afr to bounce all over. So if you set it lower than that point and then gradually raise it until it activates on decel, you can dial it in. If that's affecting you. Vac leak could be an issue...

https://drive.google.com/open?id=1zB...kGHKgzbs8EGINo my log. There is some driving, lots of decel and a long stoplight with the idle issue.

I've taken a look at your idle settings - and I think the problem is that you don't really enter closed loop usually, due to:
1) You keep your valve open out of closed loop ("Close delay (0 Means Do Not Close)" = 0). Therefore you actually don't go into closed loop idle most of the time. I would suggest setting this to 1-2 seconds.
2) Your minimum closed loop PWM is set to 32% (Idle Valve Minimum Duty(%)). In your logs we can see that this corresponds to about 1250 rpm. I would suggest lowering this value to about 23 to let the PID do its thing.

In regards to the AFR: You are bouncing in and out of idle all the time. Therefore, it might be switching between the idle VE table and the normal VE table every time it does. I would suggest disabling the idle VE Table while you are trying to get your idle in order.

Let me know if this helps - if it's still not fixed after, could you upload the latest tune and a new log?