99 IAC Woes
#1
99 Idle Woes
Hi all!
I've been reading and following this forum for the past few years I've owned my miata dreaming that I might one day get to turboing. Well, the time has just about rolled around, and I'm into my first phase of the project: swapping over to standalone. This past weekend I installed an AEM wideband along with a pnp speeduino ecu (not a megasquirt, I know, but there is decent overlap between the two in tunerstudio). I went with speeduino knowing that it is nowhere near a polished product, but I have a decent background working with arduino and wanted to give it a shot. I got the car running yesterday and got started tuning the idle as best as I can. Right off the bat, I determined my closed IAC duty cycle was around 65-70% while my open was pretty much at 100%, with large RPM differences only really apparent once I got into the 70-80% duty cycle range; I found a few other forum posts from the past few years with similar findings.
With my IAC disconnected, I can get my car to idle about 950 RPM +/- 10 RPM at ~14.5 AFR, which I am satisfied with in regards to stability but its about 100 RPM higher than I was expecting. I know that with the IAC disconnected I should be able to get the car to idle a tad under 850 RPM, and then adjust it up with the IAC/VE table. So, I'm starting to suspect a vacuum leak despite the car idling right around 850 RPM with the factory ECU. This week I plan to do a vacuum test on the entire intake side of the motor, and if I find nothing I plan to move onto adjusting the idle screw on the top of the throttle body. I'm really hesitant to do this, as I know the factory ECU was able to idle right around 850 RPM, so I'm trying to exhaust all other possibilities first.
If anyone has any other ideas they'd like to throw out, I'm all ears! I'm not asking anything on the hardware side for the speeduino, as I understand its a pretty niche product. I'm just hoping someone has had similar experience running MS or may have a tuning direction they could point me in. If anyone is curious, I can also post a log and my current tune on the car. My plan now is to really get to understand the ins and outs of the N/A tune on the car for the next 6 months before going FI. Thanks in advance for any advice!
Car is a stock 99 other than the wideband, cone filter, coolant reroute, and rad. I can even hear the IAC modulation through the cone filter.
I've been reading and following this forum for the past few years I've owned my miata dreaming that I might one day get to turboing. Well, the time has just about rolled around, and I'm into my first phase of the project: swapping over to standalone. This past weekend I installed an AEM wideband along with a pnp speeduino ecu (not a megasquirt, I know, but there is decent overlap between the two in tunerstudio). I went with speeduino knowing that it is nowhere near a polished product, but I have a decent background working with arduino and wanted to give it a shot. I got the car running yesterday and got started tuning the idle as best as I can. Right off the bat, I determined my closed IAC duty cycle was around 65-70% while my open was pretty much at 100%, with large RPM differences only really apparent once I got into the 70-80% duty cycle range; I found a few other forum posts from the past few years with similar findings.
With my IAC disconnected, I can get my car to idle about 950 RPM +/- 10 RPM at ~14.5 AFR, which I am satisfied with in regards to stability but its about 100 RPM higher than I was expecting. I know that with the IAC disconnected I should be able to get the car to idle a tad under 850 RPM, and then adjust it up with the IAC/VE table. So, I'm starting to suspect a vacuum leak despite the car idling right around 850 RPM with the factory ECU. This week I plan to do a vacuum test on the entire intake side of the motor, and if I find nothing I plan to move onto adjusting the idle screw on the top of the throttle body. I'm really hesitant to do this, as I know the factory ECU was able to idle right around 850 RPM, so I'm trying to exhaust all other possibilities first.
If anyone has any other ideas they'd like to throw out, I'm all ears! I'm not asking anything on the hardware side for the speeduino, as I understand its a pretty niche product. I'm just hoping someone has had similar experience running MS or may have a tuning direction they could point me in. If anyone is curious, I can also post a log and my current tune on the car. My plan now is to really get to understand the ins and outs of the N/A tune on the car for the next 6 months before going FI. Thanks in advance for any advice!
Car is a stock 99 other than the wideband, cone filter, coolant reroute, and rad. I can even hear the IAC modulation through the cone filter.
Last edited by pspeedy; 07-11-2022 at 12:25 AM. Reason: Made the title more applicable
#2
Why add a barrier for people willing to spend their time helping you?
I've pretty much stopped bothering to help with questions like this because it's not worth taking the time to ask. If the poster gives data that I can easily look at and use to make a definitive diagnosis then I'll try to help.
#3
I don't understand posts like this. You clarified that you're probably asking a tune question but you're waiting for someone to ask for the data that will allow us to definitely diagnose your issue.
Why add a barrier for people willing to spend their time helping you?
I've pretty much stopped bothering to help with questions like this because it's not worth taking the time to ask. If the poster gives data that I can easily look at and use to make a definitive diagnosis then I'll try to help.
Why add a barrier for people willing to spend their time helping you?
I've pretty much stopped bothering to help with questions like this because it's not worth taking the time to ask. If the poster gives data that I can easily look at and use to make a definitive diagnosis then I'll try to help.
Also, none of the map has been touched outside 0-40 kpa fuel load and 0-1500 RPM. Again, any advice is appreciated, and I'm not afraid to be told when I'm being an idiot.
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09-29-2021 03:52 PM