IAC problems - think mine is goosed? - Miata Turbo Forum - Boost cars, acquire cats.

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Old 09-27-2007, 05:49 AM   #1
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Default IAC problems - think mine is goosed?

I think my IAC is goosed, but before I bin it I want to air my thoughts incase I'm wrong!

the symptoms my car shows are

from cold it idles reletavely low i.e. 1100rpm for the 1st 30 seconds to a minute. then the idle revs steadly increase to 1400 - 1500 rpm. the Idle will then stay at that point for quite some time. (This is possibly a tuning issue, but I'm not too sure).

the coolant reaches 90degC and the idle is still at 1300 - 1400rpm. It's only after a good 15 - 20 miles *after* the coolant has reached operating temp and the engine is really properly and truely hot i.e. the intake mani is heatsoaked will the idle sit where I've adjusted it to sit at i.e. 900/950rpm.

If I adjust the idle (stock ECU is controling the idle) to be at 950 rpm as soon as the coolant reaches operating temp then after the 15/20 miles the idle sits way too low around 500rpm.

I've a gut feeling that the wax valve is fubar'd in my IAC. does that sound right? Can I circumvent the wax valve or will I run into other issues? If the whole unit is goosed can the stock ECU control the later MK2 idle valve, if it can will it fit to a MK1 TB?

I may try to re-hook up the MS to the idle valve and see if Jerry's latest settings will tune around the issue i.e. it'll alter the IAC Duty Cycle to hit the RPM targets.

Does it sound like the wax valve is shot? Can I remove it/cut it out of the equation? Circumventing it and then controling the IAC with the MS will be a damn site easier that it is at the moment.

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