Idles at higher rpm... sometimes - Miata Forumz - Mazda Miata Chat Forums
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NA (1989-1997) NA Miata discussion within. The MX5's first generation, the NA, sold over 400,000 units from 1989 to 1997.

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Old 03-03-2012, 05:39 PM   #1
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Default Idles at higher rpm... sometimes

So i dunno if this should be here or in the turbo section but here goes. Sometimes my miata idles as it should and other times is wants to idle at like 1250rpms. No rhyme or reason as far as i can tell. Hot cold doesnt matter. Ive got a turbo on it with some piping going on but i know for sure its not a vacuum or charge pipe leak cus ive fixed all thoes already. Just wondering if anyone has run into this.. im leaning twords the iac valve.. anyone have any problems that were similar related to the iac valve or maybe the maf? Oh its a 91 1.6l. It almost seems as if the iac isnt getting good coolant flow or whatever thermostatic component thats in it is sticking. Wish i could hook my scan tool to it but its too old and foriegn.
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Old 03-03-2012, 05:48 PM   #2
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Originally Posted by Dirtyturbo View Post
So i dunno if this should be here or in the turbo section but here goes. Sometimes my miata idles as it should and other times is wants to idle at like 1250rpms. No rhyme or reason as far as i can tell. Hot cold doesnt matter. Ive got a turbo on it with some piping going on but i know for sure its not a vacuum or charge pipe leak cus ive fixed all thoes already. Just wondering if anyone has run into this.. im leaning twords the iac valve.. anyone have any problems that were similar related to the iac valve or maybe the maf? Oh its a 91 1.6l. It almost seems as if the iac isnt getting good coolant flow or whatever thermostatic component thats in it is sticking. Wish i could hook my scan tool to it but its too old and foriegn.
do you have the idle valve tied into the charge piping? and there is no scanner that will read the codes heres how to get them. http://www.miata.net/garage/Engine_Diagnostics.html
ps you dont need to make the led thing they will flash on the check engine light.

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Old 03-03-2012, 05:56 PM   #3
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Yes i have the iac feeding from the charge pipe right before the throttle body. Also no check engine.. I was just saying if it was newer obdII ive got multiple scan tools i could take live readings with and actually control what the iac is doing, but being obd nothing im having a hard time figuring out what exactly is going on.
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Old 03-03-2012, 05:59 PM   #4
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do you have the time to take the throttle body off and clean it and the idle valve? because that would probably be a god first step.
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Old 03-04-2012, 10:52 AM   #5
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Yeah i suppose, I just got all the charge piping really jammed in on that side so it not like i can undo one clamp and be looking tn the tbody...
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Old 03-04-2012, 11:02 AM   #6
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Yeah i suppose, I just got all the charge piping really jammed in on that side so it not like i can undo one clamp and be looking tn the tbody...
yea mine is the same way, but that should help. oh and the t at the bottom of the thermostat can get clogged, and dont forget the piece on the side of the intake manifold.
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Old 03-05-2012, 04:15 PM   #7
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When my coolant temp sensor was on its way out a while back, it would cause idle issues, if its not your IAC, that might be something to look in to.
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Old 03-05-2012, 05:40 PM   #8
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Funny i was thinking the same thing on the way home today when i was also noticing what crap gas milage ive been getting... although ive been boostin quite a bit with the new turbo.. ill have to check it with the power probe tomorrow...

I hope thats it, its easy to check and easy to change...
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Old 03-05-2012, 08:06 PM   #9
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May want to look into changing the o2, if you do go with a wideband so you can see your afr's and it will still hook into the narrowband of the stock ecu.
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Old 03-05-2012, 08:31 PM   #10
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I wasnt aware you could run a wideband to a stock ecu... The only reason i dont have one is cus i didnt want to remove my dp and have a bung welded on cus its my daily driver...
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