lt1 high idle problem
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Teching In
Joined: Mar 2008
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lt1 high idle problem so my '94 formula has a problem, when you crank it for the first time of the day, it idles around 1500, as expected, even after a good amount of driving it idles around 1100.. will not go any lower.. the throttle blades are completely closed.. any ideas?
Probably a bad IAT sensor or TPS sensor. Are you getting any codes (IE: SES Light)?
Registered User
Joined: May 2008
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From: Chattavegas TN
clean the t/b and iac passages
run the idle screw back out till it touches the arm. The car will set its own base idle 850-900 rpm untill it gets to the point where the blades are open enough that it has to completely close the iac.
I just went through this.
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From: Decatur, TN (N-W of Athens)
That's normal. "Cold" idle is mean to be high so it warms up, then when warm it drops down between 600-800. Mine's stock idle, which I kept when I tuned it, is 600. I've seen many people who say theirs idle around 800, hence the 600-800rpm range heh
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From: Decatur, TN (N-W of Athens)
Could've been a stuck IAC that managed to break free. The up and down rpm could've been in and out movement since it couldn't open or close as far as it wanted. CD Drives are kinda like that on computers if they can't close or open all the way.
Last edited by Formula350; Jun 9, 2008 at 04:11 PM.
Teching In
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Hey I think im having the same issue with my LT1. I just put togather my 385 and when I start the motor the damn RPM's race up to about 2000k or so. sometimes higher. I have checked every possible vacuum leak, checked the TB blades, checked to make sure the gaskets were on, checked the EGR knock off plate in the back. Everything checks out. So im thinking as well it may be my IAC. So how do you check to see if your IAC is functioning properly? How do you clean it? Thanks
Chris
Chris
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From: Decatur, TN (N-W of Athens)
Pull the IAC out and see if you can push or pull it. It'll be hard, but still push in and pull out.
As for cleaning, not rightly sure other than using carb spray.
Is the computer tuned for the new engine, if not that could be the problem.
As for cleaning, not rightly sure other than using carb spray.
Is the computer tuned for the new engine, if not that could be the problem.
Teching In
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Yeah this Computer is NOT tunned for this motor. I sold the other PCM that had the tune because I thought I was going CARB. But I changed my mind and stayed with the EFI. I picked this computer up from a donor camaro at a junk yard. Now I though stock PCM would be ok to run for now, The only thing I have is the bigger cubes and a cam. Everything else is stock.
Chris
I will check those things out.
Chris
I will check those things out.
Teching In
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UPdate!!
I pulled off the intake manifold to make sure the gaskets were on properly. They were. I resealed both ends of the intake manifolds with gasket sealer. Put everything back together, TB, all vacuum hoses ie master clyn hose. Checked PCV valve. Rechecked EGR port to make sure its blocked off. I started the car and the same result has happened. Car idles at 3K RPMS. So at this point my mind is pointing to a programming issue. Your thoughts would be great thanks
Chris
I pulled off the intake manifold to make sure the gaskets were on properly. They were. I resealed both ends of the intake manifolds with gasket sealer. Put everything back together, TB, all vacuum hoses ie master clyn hose. Checked PCV valve. Rechecked EGR port to make sure its blocked off. I started the car and the same result has happened. Car idles at 3K RPMS. So at this point my mind is pointing to a programming issue. Your thoughts would be great thanks
Chris
Could be the tuning. Did you try taking off the IAC valve and cleaning it? I ran into that on mine. Check all the vacuum hoses around the intake. Try spraying some carb cleaner around there and see if the idle starts to fluctuate. I would imagine its one of those 3. The good news is you're going to need a tune anyway and the other 2 options are fairly cheap fixes. Even if the IAC is actually bad, they're only $40. I'm pretty sure that's what I gave for mine.
Teching In
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I pulled out the IAC cleaned out the passage. It has dried up oil but nothing out of the ordinary. In looking at the IAC I was not able to move it back or forward. So it seemed fine to me. When I put the intake back on I made sure all passages were sealed. The only thing that I can think of is the PCM tunning. However, On a stock tune the motor should not act that way. At least I dont think.
Chris
thoughts?
Chris
thoughts?
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1993 TA 5.7 vacuum line question. Should a vacuum line be attached to this? If so to where? I attached the blue nipple. ..didn't help....Its idling at 1,500 rpm can't figure out why???
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