fm2 kit on 90 1.6 miata with ms2, is iscv needed? - Miata Turbo Forum - Boost cars, acquire cats.

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Old 08-29-2013, 07:26 PM   #1
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Default fm2 kit on 90 1.6 miata with ms2, is iscv needed?

Hi guys I'm pretty new to the forum and the turbo miata scene in general (I wasted most of my time building hondas). I just picked up a beautiful 1990 miata with the fm2 kit on it being managed by ms2 extra (its an old alpha version 330c, I know I need to upgrade). Anyway to get to the point, I'm having a very strange issue that is really baffling me with hot restarts, let me explain:
When I start the car cold sometimes it takes a couple tries but it does fire up and idles (maybe slight hunting ~200 rpm fluctuation) around 1000 rpm, and as I drive it and it warms up to operating temperature it still continues to idle without much issue (initial drop in rpm to about 500-600 and then it finds its place back at ~1000). Now the major issue I have is if I go to start the car with out it being cold it will start but want to idle at ~500 rpm and if I touch the gas it dies. Even if I am able to keep it alive with the gas pedal anytime thereafter that I come to a stop or anything it will again want to idle at ~500 rpm. If I disconnect the ecu plug from the iscv at this point it will recover idle to ~1000 rpm and all is fine (relatively). I think I've narrowed it down to a bad iscv because of the fact that when you unplug it the idle seems to be resolved and also I took the resistance across the ecu pins on the plug on the iscv and found a resistance of 13.9 ohms and I read somewhere that the resistance spec is 12+/-1 ohms.

Now my question is this: is it possible to removed the iscv completely and run my car without it? I ask because these iscv's are pretty expensive new and who can take the gamble on a used one.
Any help you guys can give would be awesome! I want to solve this idle/hot restart issue so that I can move on to correcting the tune the car came with, but thats a topic for future post..
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Old 08-30-2013, 08:51 AM   #2
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You can remove it, but it'll never idle at the same speed twice without a lot of tuning work.

To be honest it just sounds like your ECU isn't tuned very well. Upgrade to the latest GSLender MS2 firmware and tune the closed loop idle properly, the car will idle like stock then.
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Old 08-30-2013, 09:27 AM   #3
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sounds like you need to tune your car; and that's free.
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Old 09-04-2013, 01:05 PM   #4
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Hi guys thanks for the replies, I agree I think the car just needs a good tune. But does that explain why the idle issue is remedied when I unplug the connector from the ISCV? I've attached my current tune msq file if someone could take a look at it for me and give me some pointers/maybe send me a good base map to start from, that would be awesome.
Thanks guys!
Attached Files
File Type: msq CurrentTune.msq (93.0 KB, 64 views)
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Old 09-05-2013, 06:00 PM   #5
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when the idle valve is unplugged it's held in a static position. Presently your ECU is badly tuned so causing the valve to oscillate in operation.

Post a log of the behaviour too, it's hard to see what's wrong when you only have half the story
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