Minimum(dc) very low, can't raise or lower - Miata Turbo Forum - Boost cars, acquire cats.

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Old 11-07-2010, 12:38 AM   #1
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Default Minimum(dc) very low, can't raise or lower

Here's my issue. My Minimum(dc) is set at 10, my idle screw is all the way in, and I'm almost certain I don't have a vacuum leak (checked with starter fluid and smoke).

If I raise the value the car idles up, if I lower it the car stalls when I let off the throttle. If I release the idle screw I have to also lower the value to keep the idle down.

I know I posted something similar to this earlier but I'm getting a bit desperate. Seems like all the searching in the world isn't going to answer this one.
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Old 11-07-2010, 12:40 AM   #2
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double check your fuel pressure. What rpm are you trying to idle at are the injectors known good and clean?
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Old 11-07-2010, 12:42 AM   #3
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The injectors were cleaned and flow matched when they were installed in March. The Walbro 190 was also installed new at the same time. I guess checking the FP isn't a bad idea as even new things fail but it doesn't seem too likely.

I originally tried for an 850 idle but I've since given up and I'm trying for 1K. My idle AFRs seem to be right on target, between 13.9 and 14.6.
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Old 11-07-2010, 12:46 AM   #4
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well your fpr is 13 yrs old unless your replaced it, so you might as well swap in a gauge and give it a looksie.
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Old 11-07-2010, 12:47 AM   #5
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Just for my own edification how would low fuel pressure cause this? My AFR's are spot on so it seems like the fuel is fine. Is it not a problem with the IAC having such a low duty cycle?
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Old 11-07-2010, 01:04 AM   #6
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high pressure might fprs do not just stick one way, your aic could be screwed up but that will present more of a problem on cold starts. I ran for more than a year with my aic plugged up completely out of the loop and i always idled just fine when warm or hot, only cold starts gave me a hard time. oh snap i noticed you have a SC have you checked your bypass valve that would cause a drag on the motor and could contribute to a low idle as well.
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Old 11-07-2010, 01:09 AM   #7
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The bypass valve is operating normally. I checked it recently when I was checking for vacuum leaks. Vacuum and boost are also at their correct levels. It just seems like too much air is getting into the engine and because of it I'm having to run a stupid low Minimim(dc) just to keep idle at a reasonable level. However this low setting gives me one hell of a stalling problem.

Cold starts have been a bit of a hassle but this is my first winter with the MS so I'm still working on my enrichment settings. Is there any way to test for a frozen IAC? I might pull it off tomorrow and see what I can find. I know it's doing something because I can see the car react to changes but just something isn't always right.
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Old 11-07-2010, 01:55 AM   #8
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AIC it is then i think most ms's leave the aic on stock ecu but i am unsure about the pnp you will have to set your timming to static 10 just like when you adjust your timming trigger point to set the aic properly ie mimicing the stock ecus diagnostic mode. Other wise it will not reset position and dc until the power has been cycled.
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Old 11-07-2010, 01:05 AM   #9
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Well I'm not piggybacking so the stock ECU isn't controlling anything. Never heard about having to set the timing to default to change IAC settings. When I make changes the IAC reacts immediately and doesn't require a power cycle.

I'll try setting the timing to 10 tomorrow when I work on it more. I think first I'm going to disconnect the IAC and get the car to idle correctly without it. Hell I might just leave it off. I swear I'm so sick of idle issues, everything else with the MS has been great but everytime I try to idle it correctly I run across some problem that no one else seems to have had.
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