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Old 11-27-2007, 06:05 PM   #1
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Default IAT sensor

my car was idling werid going up and down but when i take out the iat sensor it idles fine again. did i do something wrong with the installation? or do i have to go adjust something in the ecu? please help!
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Old 11-28-2007, 12:39 AM   #2
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The MS is responsible for the AIT, you sure you setup the easy therm values properly?

Does megatune show proper atmosphere temperature?
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Old 11-28-2007, 01:21 AM   #3
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As your IAT sensor heat soaks in the intake plumbing it will change your fuel mixtures. You can account for this via Air Temp Correction, it's under coolant based correction, just change it to air temp correction. I too am battling with this.
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Old 11-28-2007, 01:24 AM   #4
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you know whats wierd, even when using the GM default values my intake temp readings were still about 10 degrees off. It was reading too low, but my car idled really really good. So instead of using the 2490 ohms i used something like 1800 ohms for the bias resistor. Now that it reads the correct temp, it idles like crap just like yours, up and down. When it was reading too low, I guess it was running a tad bit more rich.

Time to mess with my VE tables.
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Old 11-28-2007, 01:26 AM   #5
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Quote:
Originally Posted by supersuk View Post
you know whats wierd, even when using the GM default values my intake temp readings were still about 10 degrees off. It was reading too low, but my car idled really really good. So instead of using the 2490 ohms i used something like 1800 ohms for the bias resistor. Now that it reads the correct temp, it idles like crap just like yours, up and down. When it was reading too low, I guess it was running a tad bit more rich.

Time to mess with my VE tables.
What injectors?
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Old 11-28-2007, 01:28 AM   #6
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Quote:
Originally Posted by supersuk View Post
you know whats wierd, even when using the GM default values my intake temp readings were still about 10 degrees off. It was reading too low, but my car idled really really good. So instead of using the 2490 ohms i used something like 1800 ohms for the bias resistor. Now that it reads the correct temp, it idles like crap just like yours, up and down. When it was reading too low, I guess it was running a tad bit more rich.

Time to mess with my VE tables.
Totally unrelated but my car likes an AFR of 13.1:1 at idle...
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Old 11-28-2007, 01:31 AM   #7
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Mine likes 12:1 for some reason. No idea why.
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Old 11-28-2007, 01:37 AM   #8
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Yeah, mines likes to idle a tad rich too 13.5-14:1. It hates to idle lean. I thought it was only my car!!
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Old 11-28-2007, 01:43 AM   #9
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13.5-14:1 would be glorious. No idea what my issues are.
What injectors are you guys running?
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Old 11-28-2007, 03:02 AM   #10
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I'm still running my stock 230cc 1.6L ones with a vortech fuel pressure riser that I had to put on since i got ripped off by slidinmiata916 on my 460cc purchase. I only got 2 injectors from atlanta, he shipped his super duper fast. Slidin Sucks dick.
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Old 11-28-2007, 03:17 AM   #11
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Ah my stock injectors idled smooth at 13.8-14.3. These high-z 550s are a different story, can't quite figure it out.
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Old 11-28-2007, 09:46 AM   #12
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Have you tried your AIC? If it thinks there is a cold start condition it will offer abit of choke but if it is not setup properly it could give to much air to quickly. It makes a huge dif in idle quality with these cars. Before i got mine right i was ideling in the 12 or so range when cold to run.
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Old 11-28-2007, 10:21 AM   #13
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Quote:
Originally Posted by cjernigan View Post
Mine likes 12:1 for some reason. No idea why.
cos you've got huge injectors. I've the same issue.

with a .1 change in PW you get a bigger AFR swing, you need it richer to stop it going too lean with each point change in pulewidth.

I found the Highres allowed me to run leaner at idle and it idled far smoother. shame it caused constant missfires :(
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Old 11-28-2007, 10:28 AM   #14
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What is deemed a good idle? how do you guys know whats smooth. For example, if I want an idle as smooth as the stock computer other then using my ears and my *** to decide if its smooth enough is there some measurement I can do.
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Old 11-28-2007, 11:46 AM   #15
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Ears and *** are about the only real measure.
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Old 11-28-2007, 05:44 PM   #16
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Ears and *** are about the only real measure.
yup, if it's smooth you know it
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Old 11-28-2007, 05:49 PM   #17
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it shoudl be pretty damn smooth,,,,,,, even with a blown head gasket: http://www.youtube.com/watch?v=HxCO3EVoQtI
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Old 11-30-2007, 04:11 PM   #18
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okay, i'm running 550cc rx7 injectors. today i found out my manifold is CRACKED!!!!!!!!! hehehe...i knew it was comming..what manifold can i get for this 16g turbo? i still can't fix my idle...i messed with vetables and got it to idle a little better but **** it back fires like a lot just randomly!
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Old 11-30-2007, 04:48 PM   #19
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Cracked Mani = Exhaust leak = wrong o2 readings = running too rich = bad idle

Man you have to make sure the sensors are reading right, by fixing up exhaust and vaccum leaks.

Even the stock ECU will struggle with a leak before the 02 sensor
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Old 12-01-2007, 08:01 AM   #20
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Quote:
Originally Posted by cjernigan View Post
13.5-14:1 would be glorious. No idea what my issues are.
What injectors are you guys running?
DSM 450's
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