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Old 02-10-2009, 09:46 PM   #1
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Lightbulb Wayne_Curr's idle woes.

(Thread split off from this one: https://www.miataturbo.net/forum/t29965/) -JP



I'm feeling the same way. With closed loop idle, I have to set it to idle at like 1100-1200 when everything electrical (lights, radio, heater) is turned off. When I turn them on, it then pulls the idle down to where it should be (~900). Even with this strategy, i'm getting idle droop when coming to a stop sometimes (yes I have a vtps)

What this means is that during a warm day when I dont need to use my heater or headlights, my idle is high. Its starting to get a little annoying. Something thats also beginning to get old is that I cant get closed loop idle to actually warm up at a higher rpm. Warmup Only works great for warming up, but closed loop only idles at like 1100-1200.

Makes me wish I had just gone parallel and let the stock ecu keep handling it.

Last edited by Joe Perez; 02-11-2009 at 09:39 AM. Reason: Thread split
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Old 02-10-2009, 10:55 PM   #2
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IWith closed loop idle, I have to set it to idle at like 1100-1200 when everything electrical (lights, radio, heater) is turned off. When I turn them on, it then pulls the idle down to where it should be (~900).
(da da da)
What this means is that during a warm day when I dont need to use my heater or headlights, my idle is high.
Feh?

In closed-loop mode, your idle RPM should be constant whether it's a mild afternoon (no loads) or a searing hot night (A/C & headlights on). You might get a little droop when you first turn on the load, but the steady-state idle RPM should be the same regardless.

What's your Min(dc) value, and what's the typical DC observed in the log during normal (lo load) idle?
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Old 02-10-2009, 11:02 PM   #3
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Feh?

In closed-loop mode, your idle RPM should be constant whether it's a mild afternoon (no loads) or a searing hot night (A/C & headlights on). You might get a little droop when you first turn on the load, but the steady-state idle RPM should be the same regardless.

What's your Min(dc) value, and what's the typical DC observed in the log during normal (lo load) idle?
To start, i've been playing with the dc values (min and closed) to try and see what a difference they make. Right now they are min:24 closed:22.

I should also note, changing the fast and slow rpm idle numbers doesn't change a thing.

Looking at a log, looks like idledc sits steady at 22.
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Old 02-10-2009, 11:10 PM   #4
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I should also note, changing the fast and slow rpm idle numbers doesn't change a thing.
Then something is wrong. Let's have an MSQ and a log showing some warm, no-load idle, then some warm idle with full load (A/C, cooling fans on, blower at max, headlights, etc).
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Old 02-10-2009, 11:13 PM   #5
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Then something is wrong. Let's have an MSQ and a log showing some warm, no-load idle, then some warm idle with full load (A/C, cooling fans on, blower at max, headlights, etc).
5 mins, i'll pm it to you so i dont junk up this guy's thread anymore.
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Old 02-10-2009, 11:24 PM   #6
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Sorry OP, cant seem to attach to a PM. We seem to be having the same issues anyway =P

Joe, my engine has been sitting for 15 mins so its not all the way hot so this isn't as dramatic as it would normally be, but you can clearly see the idle high with no load, and low (800-900ish) with high load. I hit the throttle a couple times but it wouldn't droop for me.
Attached Files
File Type: xls datalog200902101916.xls (94.8 KB, 61 views)
File Type: msq new tune18.msq (35.1 KB, 75 views)
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Old 02-11-2009, 09:46 AM   #7
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In that log, IdleDC is sitting at 22 the whole time. It's never even getting into closed-loop idle control.

Try reducing the Closed(dc) to 16, and Minimum(dc) to 18. See if that gets any activity out of it. These numbers are probably too low, but it's just a test for now to see if we can make it do something other than sit there with its thumb up its butt.

You can swap one of the gauges in the MegaTune dashboard to IdleDC so you can watch in realtime what the idle controller is doing.
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Old 02-11-2009, 03:18 PM   #8
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Alright, i'll give that a shot today. As an update, yesterday I played with my idle screw and the idle seems more steady, albeit high. I'm going to re-read the manual on PWM idle as well. I'm not understanding it as well as I need to.
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Old 02-11-2009, 04:12 PM   #9
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idling in my car right now the gauge just sits at whatever value is in the closed DC box. What kind of behavior should I be observing here?
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Old 02-11-2009, 04:30 PM   #10
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Ah ha! When you tweaked the air screw on the throttle body, you probably let in too much air. Even with the IAC valve sitting there closed, the RPMs are not dropping low enough for the MS to start trying to control it.

Turn the screw back to where it was, set the numbers in MS like I said, and let's see another log. Hopefully we'll have some activity on the idle controller.

If you find (by watching the IdleDC gauge in MT) that the idle controller is just sitting there at either the Min or Closed value, then you have too much air bypassing the solenoid, and the RPMs are remaining so high without it that it isn't even bothering to activate.

Once you've got it idling in closed loop, you want to observe the smallest number that IdleDC commonly runs at (warm, with no load) and set the Min(dc) number either equal to or one less than that. This will lessen the droop when returning to idle from cruise, as the idle circuit will start out at a reasonable number, rather than starting too low, undershooting, and then having to recover.
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Old 02-11-2009, 05:46 PM   #11
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Ok, playing with it right now and I dont think PWM is working right at all. If I turn the idle screw down, it just gets lower and lower until it wants to die or just dies.

The idle DC gauge isn't showing anything other than what is in the closed loop box.

Edit: I should throw in some history on my idle issues.

First, it idles fine with the stock ecu but droops BAD when exiting the freeway and pushing in the clutch after a period of sustained RPMs.

Second, when I built my MS, I had left out the insulator on the TIP120. This caused my car to idle at 3k no matter what I did. Needless to say i've put the mica insulator in and now it seems to idle more normal than ever.

So at this point i'm wondering if the damn thing is working at all right now. How can I test this with my multimeter?

Last edited by wayne_curr; 02-11-2009 at 05:58 PM.
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Old 02-11-2009, 06:15 PM   #12
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if you unplug the idle valve (while idling) is there a change?
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Old 02-11-2009, 08:01 PM   #13
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So I cant unplug my valve while running because i dont have the tbelt cover on, tried but almost lost a finger.

I did, however, unplug with it off, turn it back on and it was being weird. Seems like the car just wanted to stay where I revved it kinda. In summation, it sees that the idle valve is working atleast somewhat.
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Old 02-12-2009, 04:24 PM   #14
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Could my TIP120 be bad? It seems the idle valve itself is working. Not sure where to go from here. The idea of having actual working closed loop idle gives me a boner.
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Old 02-12-2009, 05:01 PM   #15
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Does your multimeter have a frequency setting? If so, try scoping the frequency between the IAC wire on the MS and ground, and see what you find.
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Old 02-12-2009, 08:47 PM   #16
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Does your multimeter have a frequency setting? If so, try scoping the frequency between the IAC wire on the MS and ground, and see what you find.
I have a cheap MM and unsure if it has a scope setting. If this is something you'd find only on nicer MMs, I dont have it. I'll check though.
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Old 02-13-2009, 12:31 PM   #17
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I should have just said "measuring" - to do this test, it doesn't need to plot the signal like an oscilloscope, just measure the frequency.
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Old 02-14-2009, 08:35 PM   #18
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So I was just looking through my settings.ini file to see why my car wont run without my AFM (still working on figuring that out) and I noticed that MT was set for a stepper iac! Wtf?! Changed that to PWM, going to go out and see if that was the plobrem.

Edit: nope, didn't work. And as for checking the frequency, i dont think my MM is cool enough. Either that or I dont know which of the little symbols tests freq. And the car runs fine w/out the AFM, just accidentally unplugged my GND->FP jumper.

Last edited by wayne_curr; 02-14-2009 at 09:08 PM.
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Old 02-15-2009, 09:39 PM   #19
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I'm actually having similar issues as well with my MS1 build. The IdleDC value never changes so in order for my car to idle less than over 2k RPM, I just leave the IAC valve disconnected and adjusted my idle screw to give me a nice 850 RPM idle speed. As soon as I reconnect the valve, it shoots back up and never changes.

I have check the continuity and everything on my TIP120 and it checks out fine.

Any ideas?
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Old 02-16-2009, 12:25 PM   #20
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Could you please post your MSQ, Karter74? I can have a look at the settings. Also, how exactly is the IAC wired up in your parallel install?
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