Funky idle, halp!
 

So the car got dyno tuned not too long ago and runs hella strong. The only thing I cannot figure out for the life of me is a funky idle issue.

After a cold start I have to keep the throttle depressed about half an inch for about the first 5 seconds to keep it running. If I don't it'll shudder and stall. (Semi) warm starts are no problem.

When idling (be it warm or cold) it oscillates between 900-1200 rpm in a smooth up-and-down kinda way. Not jerky or lopy idle, just smoothly going back and forth. It never dies/stalls, it just idles all day long like this.

I have changed and tried loads of settings, adjusting idleDC, PWs, spark and fuel maps to no avail. Tried the base idle setting on the throttlebody but this only changes the rpm band where the oscillation happens.

This is about the last thing to finish up and get it to stock drivability, but with more power.

Attached the latest .msq that it's running right now and a log I did today.

Thanks for any input :)

sounds like you need to tune ASE and warmup....

I figured that too for the cold(er) starts. However, this shouldn't affect warm idle funkyness

I am a TECgt user so am not familiar with your particular ECU but I would try switching off the AFR feedback first and see what happens. Does the ECU you are using attempt to target the rpm idle speed by varying the advance? Again try switching it off to see if that is causing the idle oscillation.

EGO corrections don't kick in until 1500 rpm, so below that it's running of the fuel table. Ignition in the idle cells are at 18 degrees of advance. Playing with this didn't do any good to the oscillating.

I have a feeling it's the idle DC that needs tweaking, but I think I have tried about everything so far, to no avail

OK, as I say I am not familiar with the ECU you are using so you'll have to forgive me if I am barking up the wrong tree...

Anyhow I also have the idle cells set to 18 deg advance but to fine tune idle speed the TEC has the option of varying the idle advance, I have mine set to 3 deg per 50rpm off target. If you have a similar setting then you could try turning it off to stabilise idle advance.

TBH it took a little time for me to get the idle on the TEC smooth with error and rate of change sensitivities, idle reset and min and max duty cycles among other things to get right. Error and rate of change sensitivities had biggest affect on idle oscillation.

Good luck with it.

tried, tried and tried again. No dice. The oscillating is less, but still there. Maybe try closing the idle screw on the TB and try again from there. We'll see.


Slowmx5: seeing your sig, weren't you on a klm flight from amsterdam to heathrow somewhere late last year? (october, november-ish) We had a talk about turbo miatas as I was reading maximum boost (again...) Might be a long shot, but hey...

Try this:

1. Go to Crank / Warmup -> After Start Enrichment Settings.
2. Change Fixed MAP value to about 10 kPa lower.
3. Burn this to the ECU.

Let me know if that makes it better or worse.

No not me although, having just checked your sig, I see we are not too far apart. Hope you get it sorted.

Do you run 550s? If so you could look at my map.

I run the stock 265s. I wanna see your map anyway and take a look at your idle settings. We both run (more or less) the same motor so I want to get a ballpark figure for the IAC settings. We'll discuss on thursday at zandvoort tho :)

Sorry to dig up a dead thread, but was this ever solved?

My idle issues are exactly the same as oscar and we are both NA (though aside from COPS and MS my engine is bone stock).

I have just tried Matt's suggestion of changing the fixed_MAP value from 80 to 70 and this seems to help the cold starting issue. Oscar yours was 123! which isn't even on your VE table which might be causing your problem.

I have posted my .msq and a short log of Idling during which I turn fans and lights on and off.

I have a feeling that it could just be down to a shitty tune.

One other interesting thing is that when running warmup idle control my fast idle DC is 24 and my slow idle DC is 23. Under normal conditions my slow idle is about 900 and fast is about 1200. This seems a huge difference in rpm for a 1% DC change. Is this normal?