Restoring idle control to the OEM ECU - Miata Turbo Forum - Boost cars, acquire cats.

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Old 12-28-2009, 10:47 AM   #1
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Default Restoring idle control to the OEM ECU

Over the weekend I swapped back to "stock" in order to pass MD state emissions testing. The Adaptronic ECU is now completely out of the loop, with the stock ECU controlling the idle, which is now infinitely better than anything I've been able to obtain with the Adaptronic.

When I plug the Adaptronic back in, how can I bypass it's idle control? Looking at the FSM, it appears there are just two wires that connect the stock ECU to the IAC, 2M and 2O (or 3M and 3O, can't recall). Is it as simple as putting these back in the loop to the factory ECU or am I missing something?

What's throwing me off is there's just one wire dedicated to IAC control in the Adaptronic literature, which is Aux output 1. If I snip that before it makes its way to the Adaptronic unit, what do I have to connect it to?
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Old 12-28-2009, 10:50 AM   #2
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The oem ecu will need to see all the other signals (cas, ait, clt, etc.) or it wont know what to do and just spit CELs.
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Old 12-28-2009, 11:09 AM   #3
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The stock valve gets engine-on +12V from 3M and a pulsed ground at 3O. There would be no reason to interrupt 3M.

As I understand, the adap locks stock AIT and CLT to a fixed value. This probably does not bode well for allowing the stock PCM to control idle.

You may find that opening the mechanical bypass a bit more will do wonders for idle.
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Old 12-28-2009, 11:57 AM   #4
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to idle, he stock ECU needs:

TPS
IAT
CLT
A/C trigger
Power Steering trigger
RPM

and maybe MAF, but I dont think so.
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Old 12-28-2009, 01:54 PM   #5
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Pat,

What fuel injectors are you running? Can the factory ECU handle idling 600cc or 550cc injectors?

If it can... then I would be curious to do the same thing... I had a horrid time in traffic this weekend with my idle issues...

Cheers,
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Old 12-28-2009, 02:40 PM   #6
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I doubt the oem ECU can handle 600cc injectors. I wish I could leave cranking and idle to the factory ecu.
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Old 12-28-2009, 04:38 PM   #7
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Thanks guys, it seemed too easy.

Matt, I'm back on stock injectors for the week in order to get through VEIP.

When I installed Xede a few years back I tried running the 550ccs on the stock ecu; no luck.
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Old 12-29-2009, 05:14 PM   #8
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Does anyone here have their idle/cold start sorted so they can honestly say its like stock again?
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Old 12-29-2009, 06:45 PM   #9
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y8s says his cranks and catches quickly. I'm definitely envious of that. Still waiting on my 600cc injectors and other bits so I can fully use some of the better maps that have been posted.
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Old 12-29-2009, 10:43 PM   #10
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Not like stock yet, but getting closer...

hot starts (like just recently shut down), almost like stock
warm starts, sometimes it cranks quite a bit, but I have to turn the key no more than twice to get it to catch anymore.
cold starts, same as warm but a little easier, but I've got my crank fuel set to 142 @5* C as of today... Does that sound reasonable? Does it really need that much fuel when it gets cold? I'm on stock injectors...

Warm idle, nice and steady at 900-950... Headlights or other elec. load makes the idle drop to about 600 then slowly recover back to 900 or so. Gotta work on that. Very slight hunting.
Cold idle, right after start, it idles very low like 500 or so if I don't help it, then wakes up and idles perfectly after about 5 seconds. I can start it and get it to idle without touching the gas down to 0C so far.

I'm not sure what I'm doing wrong with enrichments for the cold start/idle that don't let the rpm's jump up faster...
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