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Old 12-15-2010, 03:50 PM   #1
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Default Cold weather equals high idle???

Hey guys ! ! !

Don't beat me up too bad as I'm very new to turbos. I am the new owner of Dan's Miata (Dan's Creation) and this incredibly cold weather in Florida is playing havoc with the idle. The car idles at 2600 most of the time and when it's not it revs up and down between 1600 and 2600. This is real annoying at stop lights. I've checked the throttle return and it is working properly with no sticking. I know I have lead in my right foot, but the high reving happens even when I'm not in the car!
For reference:
- 1.6 motor
- Greddy Turbo Kit (TD04 15G)
- Greddy Intercooler (anodized black)
- Custom Intercooler Piping
- Turbo Tony 2.5" Downpipe (w/flex coupler)
- DP6061 2.5" Exhaust (magnaflow muffler)
- 1.8L Injectors
- Walbro 190lph Fuel Pump
- Stock ECU

The car ran great prior to this cold weather (20's night - 50's daytime). Thankfully the weather is getting warmer and maybe the idle issue will go away. Any help is greatly appreciated.
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Old 12-15-2010, 04:08 PM   #2
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If it is on the stock ecu and the IAC is plugged in and working. I think you only have the idle screw adjustment to mess with. however, I working IAC is supposed to handle this.

Unplugged the IAC when it is a cold, and then again when warm noting if anything changes.

EDIT: You've got to have a few other computer items if you are running the stock ecu. How are you controlling fuel and timing while in boost?
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Old 12-15-2010, 04:10 PM   #3
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should be the same...probably a bad valve.
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Old 12-15-2010, 04:26 PM   #4
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Quote:
Originally Posted by djp0623 View Post
If it is on the stock ecu and the IAC is plugged in and working. I think you only have the idle screw adjustment to mess with. however, I working IAC is supposed to handle this.

Unplugged the IAC when it is a cold, and then again when warm noting if anything changes.

I'm at work and not able to get to the car. Where is the IAC located and how do you unplug it?

EDIT: You've got to have a few other computer items if you are running the stock ecu. How are you controlling fuel and timing while in boost?
This is where I can use some help too. I know there is a fuel management piece located on the passenger side of the block, but not sure if it's adjustible or not. The previous owner did not tell me or list of any timing control devices on the car. He prepared a very nice car and it is well known in the Miata community.

Thanks for the advice ! ! !
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Old 12-15-2010, 04:30 PM   #5
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Originally Posted by Braineack View Post
should be the same...probably a bad valve.
A bad valve? Please explain.

I've read your write up regarding building a MS and I plan on having you build one for me early next year. Please let me know what info you need from me. I heard that running the stock ECU can be dangerous, but the previous owner did the install 2 years ago with no issues other than the O2 sensor going bad occationally.

Thanks for the advice ! ! !
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Old 12-15-2010, 08:37 PM   #6
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Check for a vacuum leak.
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Old 12-15-2010, 09:03 PM   #7
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What year is the car?

90-93 have four possible ways for air to get in (other than the throttle):

1. Idle Speed Control Valve (ISCV) -- Controlled by ECU.
2. Air Valve -- Dumb Device Controlled by Water Temperature (like a T'stat)
3. Idle Adjustment Screw -- Controlled by Your Hand on a Screwdriver
4. Vacuum Leaks -- Controlled by Wear, Tear and Ineptitude

A really nice write-up, with pictures, is here: http://www.miata.net/garage/isc.html
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