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Old 02-24-2010, 10:22 PM   #1
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Default can I idle the car without the IAC plugged in and no TBS updated

I have a SC kit from a 97 engine but my car has 91 wiring. The IAC provided by the SC kit does work with the 91 plug. I seem to have a couple of options.

1.) hack the harness up to plug into the SC kit's IAC - that is assuming that the IAC is controlled similarly from the 91 and the 97 (which i have my doubts)
2.) run without the IAC - MS should be able to overcome this with MS i might just have a much higher idle


edit update:

can i run the car without the TBS also what does MS do with the TBS since the 91 only gives off 2 signals WOT and closed

Last edited by thewatcher101; 02-26-2010 at 03:18 AM.
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Old 02-24-2010, 10:51 PM   #2
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You can get it to idle decently but it won't catch itself when there is increased or heavily decreased load. Like when you clutch in quick to come to a stop you might have to modulate the throttle to keep it running. If a/c kicks on it might stall at idle. Things like that where the IAC is really necessary.
What SC kit?
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Old 02-24-2010, 11:34 PM   #3
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FFS coldside - funny thing is that they advertise its stock idle since they put so much into design a external IAC for the kit - but i don't need it - I don't have AC so that is not an issue

mm...... i think i can just set a high idle like 1500rpm so it doesn't stall out even when clutching in maybe.....


well if i can't find a clear solution - i think my best bet would be to cut my harness to see if it works with the 97 IAC - if that doesn't work i'll just end up unplugging in and have a crappy idle

the car is driven like once or twice a month to autox events - not too worried about the daily drive or anything like that
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Old 02-25-2010, 12:39 AM   #4
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Just splice the harness. Since you have a MS you just need to figure out the settings for the valve. The IAC in my car is actually out of a volvo and i just used MS to make it work. Also if your ms is a diy make sure you do the PWM idle mod.
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Old 02-25-2010, 11:57 AM   #5
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sweet, did some research i think the IAC valve reading is the same for both 1.6 and 1.8 just repackaged since the resistance of a cold IAC valve for both is around 12

here are the sources

If you have a 1

i have mspnp


now the other issue and last one with this install to jump over is the TBS - The TBS on the 91 is not the same as the 97 -

these two units are not the same at all the 97 is a continuous resistor that can tell what angle the throttle is - while the 91 is just a switch that pretty much tells when it WOT or closed

Last edited by thewatcher101; 02-25-2010 at 12:14 PM.
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Old 02-25-2010, 06:17 PM   #6
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decided to not add the IAC - since it was going to be a big pain for more then it is worth - the car is driven a few times a month

what adjustments do i need to make - so my car doesn't stall when i let go of the clutch - and how would my cold start be effected
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Old 02-25-2010, 07:21 PM   #7
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I run a 2004 engine in my 1990 with ms and all i did was open the idle screw all the way and I idle at about 1100 Rpm and all i run is alt. no ps or ac.... my iac was broken so i just opted to go without. if it still stalls when you let off gas and put in clutch then try changing the the butterfly valve stop (this is not really ideal) (only move it like a quarter a turn at a time and write down how many quarters you turn it so you can easily put it back to stock for whatever reason).

I did the harder thing and put that dampening thing from the 90 TB onto my 03 TB to keep it from slamming shut. There are many solutions really and depend on the car. Try just moving the idle screw some and see how that goes for starts would be my recommendation as that solved it for the most part for me.

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Old 02-25-2010, 10:06 PM   #8
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okay i will try that - since I am not running the IAC anymore do i have to go in to change anything in MSPNP?

I have the BBK 75mm TB - and I will play around with that.
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Old 02-26-2010, 02:26 AM   #9
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I can't speak for PNP because i tuned my MSII from scratch with the intent of not using IAC (meaning i ignored anything labeled IAC in instructions haha) but i would imagine it would be fine until you mess with the throttle stop screw then you need to re calibrate the TBPs (again yes changing that screw will fix your problem but is not a good solution!)

The Idle screw you should be fine to play with as much as you like though, so try that and see what you can get. the big concern is really what happens when you go WOT and then take your foot of the gas entirely... you will stall more than likely with stock idle screw position.

Do all of this with the engine at operating temp too. If you do it cold your idle will be way too high at operating temp. You will not be able to get a good cold idle no matter what either, just warning you. You will have to keep your foot over the gas pedal to catch if from stalling for the first min (i have managed to work it down to just the first 20 seconds even on the coldest mornings after alot of work).
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Old 02-26-2010, 03:08 AM   #10
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Old 02-26-2010, 03:20 AM   #11
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I live in socal temps don't dip that much lower and car gets driven few times a month so not too worried.
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Old 02-28-2010, 09:26 PM   #12
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You should be just fine then.
[rant]
no disrespect intended, so many just act like I am desecrating the miata community for not running an IAC. In your eyes I might as well just rice??
[/rant]

Last edited by noth1ngmuch; 02-28-2010 at 09:48 PM. Reason: rant shorted some haha
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