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Old 03-01-2014, 09:53 PM   #1
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Default high idle right after startup

I'm running a diypnp in my 93 miata with 99 motor complete with the 99 throttle body. I recently switched to closed loop idle, and it idles just fine, but right after start it goes to 3k then drops to 2k (slightly oscillating along the way) then settles at just under 1k like I want it to. Ive played with after start enrichment but doesn't seem to have any effect. It was also taking a long time to crank until I copied the crank settings from the 99-00 basemap and that seemed to fix that, but now I have this high idle issue. It does it hot or cold, but seems a little worse when cold. I'd post my msq and log but I'm not at my computer right now, plus I'm still using the stock O2 (LC1 coming in a few days). Coukd it be because of the narrowband? Just wondering if anyone had any suggestions as to be here to start looking. I'm pretty new to tuning, but have been learning more and more each day since I installed the computer a week ago. Other than that the car seems to be running great.
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Old 03-01-2014, 10:01 PM   #2
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tune your idle.
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Old 03-02-2014, 03:45 AM   #3
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try adjusting it
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Old 03-02-2014, 09:24 AM   #4
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Try lowering Crank to Run Taper.

Start Up/Idle>Closed Loop Idle PID Settings>Crank to Run Taper.

The value is in seconds. This is the time MS will take to taper from your "PWM Idle Cranking Duty" Cycle to your desired Idle Duty Cycle. Decreasing the value will caue it to taper down to your target faster. Reducing it too much will cause the car to start, run for about 3 seconds and then die. Play with the settings until you get it to where you want it.

For what it's worth, you may also need to address your Cranking Duty Cycle and Cranking Pulsewidths. Starting and jumping up to 3k is not an entirely great thing for an engine. Likely you'll want to decrease both of those tables to get the start up RPM a little lower. (2k-ish is fine)

PWM cranking duty cycle is how far open the IAC motor is, which would be equivalent to how far you are opening the throttle body, if you were doing so with your foot. So the fact that you are shooting up to 3k means the IAC is open too far and letting in too much air. When you lower this value and remove air, you will also need to remove fuel to ensure a clean start up. Cranking Pulse is the amount of fuel to injector during cranking dependent upon coolant temp, so you'll want to decrease these values as well.
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Old 03-02-2014, 09:59 AM   #5
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Thanks StratoBlue. Some very good info for a noob like me. My crank to run taper was set by default to 3 seconds. I lowered it to one and it didn't make any difference. I will try your suggestions, thanks!

Last edited by wkndracr; 03-02-2014 at 04:26 PM.
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Old 03-03-2014, 10:11 AM   #6
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Looks like lowering pwm crank duty did the trick. It still oscillates a bit before settling at about 860 rpm, but I can live with that for now. It started fairly easily this morning too, considering it was 20 degrees. I still got a stutter while cranking for a while, where it sounds like the starter is going backwards for half a crank. Could that be a timing advance issue, or just because it's cranking longer than normal? Other than that, I am pretty happy with it considering I've only been at it for a week. Just gotta keep tweaking. Wideband O2 should be going in today after work.
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Old 08-15-2017, 01:03 PM   #7
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rather than creating new topic I will bump this old one...
I have the problem with my car with Idle. I have MS2 enhanced from MSlabs.
On cold start it idles around 1500rpm, when cold mornings or night even over 2000rpm. I am novice with the standalone ECUs, so I would like to hear more than just "adjust your idle", that is obvious.
After I let it idle for like 10-15seconds it goes to my set value which is about 1000rpm. I use Speed density, but I do not have Air temp sensor for now. This problem shows up also when I cruise and I stop on the trafic lights or somewhere and put it into neutral. It holds 1800 or so RPM and then after while goes back to 1000. Another thing is that, sometimes when the car is cold, first few meters car is able to pull with gear in at about 2000rpm without my foot on the gas. Sometimes there is also problem, mostly when the car is hot that when release the throttle pedal and in the gear, above 30kpa (which is above what I have set for fuel cut) the fuel does not want to cut off. it is still about 15-18 sometimes about 20AFR but my AFR gauge never see 22.4 or so which is max it can read, so it is really off. It is nice that when the exhaust is hot it bubbles into it but I do not want this bahaviour....I know this is quite a lot of problems but I believe they are all related to one thing (other than my little knowledge about ECU tuning :-) )
I can make a logs if someone would be so nice to help me out with this, I am actually open to pay if someone is able to solve my problems....I will study the ECU tuning more over this winter as I plan to finally install ITBs, but I still want to let it tune by professional, I just want to be able to understand things more... Please do not kill me with answers like you should study thing and so on. I am not pro engine builder I do not own race shop and I do not spent ours behind steering wheel and under/in car. I like to learn about things but i do not have as much time as I would like to because of my work which is my biggest interest at the moment, so...Any help is much appreciated
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Old 08-15-2017, 01:12 PM   #8
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Quote:
Originally Posted by AndrewG View Post
rather than creating new topic I will bump this old one...
I have the problem with my car with Idle. I have MS2 enhanced from MSlabs.
On cold start it idles around 1500rpm, when cold mornings or night even over 2000rpm. I am novice with the standalone ECUs, so I would like to hear more than just "adjust your idle", that is obvious.
After I let it idle for like 10-15seconds it goes to my set value which is about 1000rpm. I use Speed density, but I do not have Air temp sensor for now. This problem shows up also when I cruise and I stop on the trafic lights or somewhere and put it into neutral. It holds 1800 or so RPM and then after while goes back to 1000. Another thing is that, sometimes when the car is cold, first few meters car is able to pull with gear in at about 2000rpm without my foot on the gas. Sometimes there is also problem, mostly when the car is hot that when release the throttle pedal and in the gear, above 30kpa (which is above what I have set for fuel cut) the fuel does not want to cut off. it is still about 15-18 sometimes about 20AFR but my AFR gauge never see 22.4 or so which is max it can read, so it is really off. It is nice that when the exhaust is hot it bubbles into it but I do not want this bahaviour....I know this is quite a lot of problems but I believe they are all related to one thing (other than my little knowledge about ECU tuning :-) )
I can make a logs if someone would be so nice to help me out with this, I am actually open to pay if someone is able to solve my problems....I will study the ECU tuning more over this winter as I plan to finally install ITBs, but I still want to let it tune by professional, I just want to be able to understand things more... Please do not kill me with answers like you should study thing and so on. I am not pro engine builder I do not own race shop and I do not spent ours behind steering wheel and under/in car. I like to learn about things but i do not have as much time as I would like to because of my work which is my biggest interest at the moment, so...Any help is much appreciated
PM me if you're serious about the above. I'm currently tuning a bunch of Miata's and can help you out if you want.
To try to address each of your questions would take a whole book worth of information, because first we'd have to teach you at least the basics of tuning.
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Old 08-16-2017, 06:05 PM   #9
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PMd
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