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Idle Valve

 
Old 10-25-2016, 06:27 PM
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Default Idle Valve

Hello all. I have the FMII kit on my 99 miata with the 36-2 trigger wheel. I'm having issues with my Idle Valve %. With the screw all the way in I can only hit a max of 23% at an idle of 850RPM. Timing is about 12 degrees. If I back the screw out a 1/2 turn it hits 14.9%. Timing drops to 11 degrees. The motor vibrates more with the idle screw all the way in. I built a pressure tester and put it on my turbo. My intake will hold 5psi steadily for a few minutes.

My question is what Idle Valve % valves do you typically see and how do you adjust your idle screw?

Thanks.
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Old 10-25-2016, 07:19 PM
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I believe Jeremy recommends a IAC duty cycle of between 30-35%. I'd remove the intake pipe and the air idle adjustment screw and hose everything out with throttle body cleaner. It could also be a vacuum leak somewhere post throttle body. Grab a can of ether (starting fluid ) and go looking for the leak. Fred B
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Old 10-25-2016, 07:33 PM
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Pages 15-16 of FM Hydra manual . You do have copy right ? If not you can download from Fm's site under the support tab .
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Old 10-25-2016, 08:09 PM
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Do you remember if you had to almost bottom out your idle screw? What was the highest % you were able to achieve?

Thanks
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Old 10-25-2016, 08:47 PM
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I'm at least a couple of full turns out from being bottomed . I'll check it later this evening and get a firm number , but it is one of those things that's going to vary car to car . Pretty sure I've seen mid to high 40s duty cycle when I was mucking with it. Fred B
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Old 10-25-2016, 09:42 PM
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Could you pop off a vacuum line and see if your car drops to 14.9% or if it stays a little higher, maybe 16%? I'm trying to gauge how big my leak must be.

I just now soaked my intake, injectors, and throttle body with an entire can of ether and nothing happened. I tried my best to shoot it under the intake. I shot a single squirt into the air filter and it dropped in RPMs. After I did the squirt, the AFR stayed down at 12.5~13 for 5 minutes. I then turned the car off and on and it jumped back to 14.7.

Another issue I've experienced is when I stop at a red light the car idles at 2,000 or 3,000 RPM. What makes it really weird to me is that it's exactly 2,000 or 3,000, not 2,200 or 2,700. Reving the car up doesn't help. It'll fix itself if I continue driving and stop at the next light. Turning the car off and on will fix it as well. I'm debating on buying another throttle body. Do you run a stock throttle body or do you have the skunk?

Thank you very much for your help.
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Old 10-25-2016, 10:05 PM
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My idle screw is 1 1/2 turns out. Stock NB throttle body Try bypassing your PCV valve ( unplug it from the manifold and cap the manifold port ) then go for a drive and see if the behaviour changes. Ive had similar symptoms with a bad PCV valve .I don't have my tuning laptop with me this evening so I'm somewhat limited to what I can do tonight. Fred B
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Old 10-26-2016, 10:10 AM
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fjs, I do not think you have a vacuum leak. Try recalibrating your TPS. Perform the calibration procedure at least twice, calibrate closed, calibrate open, calibrate closed, calibrate open. I have seen the TPS closed value change a point or two on a second calibration.

If this does not fix it, manually lower the closed calibration value by 1 unit.

I like to set the Idle Valve value in the 27% to 30% range. This is a little lower then Jeremy suggests, but I find by running this low the idle speed is less likely to oscillate when the AC is on.
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Old 10-31-2016, 07:02 PM
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Originally Posted by Ken Hill View Post
fjs, I do not think you have a vacuum leak. Try recalibrating your TPS. Perform the calibration procedure at least twice, calibrate closed, calibrate open, calibrate closed, calibrate open. I have seen the TPS closed value change a point or two on a second calibration.

If this does not fix it, manually lower the closed calibration value by 1 unit.

I like to set the Idle Valve value in the 27% to 30% range. This is a little lower then Jeremy suggests, but I find by running this low the idle speed is less likely to oscillate when the AC is on.
Hi Ken, I manually lowered the closed calibration value by 1 unit and it did help, but not enough.

I was able to find another throttle body and I installed it on the car reusing the old gasket. I calibrated the TPS at 30, my other throttle body calibrated at 23. With the idle screw turned all the way in I'm at 29.8%! Improvement! 1/4 turn out and it sits at 27.45%. I'd like to use my old throttle body, so I'm going to swap the TPS sensor.
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Old 10-31-2016, 07:44 PM
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While swapping the TPS sensor onto my original throttle body I noticed a little bit of light peaking through the top of my butterfly valve. I adjusted the screw until I couldn't see any more light.

Idle screw all the way in 38.82%.
1/2 turn out 36.08%
1 full turn 32.94%
1-1/4 31.37%
1-1/2 30.2%

With the throttle body on my car I couldn't see the slight gap.
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Old 11-14-2016, 08:13 AM
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I had the same issue. I pulled the throttle body to give it a thorough cleaning and, after reading this thread, looked for any light coming around the butterfly when the throttle body was "closed". Saw that it was slightly open and, after giving it a good cleaning, adjusted the stop screw so it would really be closed. After reassembling it I re-calibrated. The previous off throttle calibration was 27 and post adjustment it dropped to 24. My duty cycle for the idle air screw now is where it needs to be. I set it at 28% following Ken's advice.

Now I still have to deal with the idle oscillation with the A/C on. It has improved with the idle adjustments but still there. The change is that it formerly went from 2,000 rpm to nearly stalling and now it oscillates between normal idle and about 1800, but more slowly and a little "softer".

Some more tweaking is called for. Anyone have a suggestion (aside from Megasquirt)?
paul
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Old 11-14-2016, 10:11 AM
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Paul, how much are you increasing your idle speed when the AC compressor turns on? I think i have mine set to 100RPM. I get no stalling and 1 to 2 oscillations when it starts, but not every time.
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Old 11-14-2016, 02:35 PM
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Hi Ken,

I'm not sure....would that be under the Idle Speed Control Settings? Choices there are, ISC P Term, ISC I Term, Thermofan On ISC Target Trim, and Moving Vehicle ISC Target Trim. Those last two show their values as rpm. If they are the right settings, then my P Term is 100, the I Term is 20, the Thermofan on is 0 and the Moving Vehicle is 200.

Other than that, the only idle speed A/C control I see is the AC Clutch Idle Speed Target Trim. Those settings are at 200 across the entire temperature range.

Someone suggested the applicable PID controller. I haven't quite wrapped my brain around that yet. I've been recovering my properties from flooding following Hurricane Matthew and the Miata and it's brand new Hydra haven't gotten much attention. I'm still trying to learn the software.

Thanks for your input. I know that you do this for a living and I value your advice.

Paul
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