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Old August 21st, 2013, 03:11 PM   #21
wave_crusher
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Iac

You can use a multimeter to see if it is bad; I don't remember what you actually need to look for...just run to advance or autozone and look in one of their Haynes manuals.

The manual way that I know is to screw the end out all the way and start up your truck, it will probably die right away or idle very low. If the IAC is good then it should smooth out or at least go back to what is was before you screwed out the end of it. If the IAC doesn't move then it needs to be changed

I wouldn't think it's the TPS, in my experience a tps would just make the truck idle shitty, but once you're driving it would seem normal







....or maybe i am mixing up the two???? lol It's been awhile since I worked on a TB 350

Last edited by wave_crusher; August 21st, 2013 at 03:18 PM.
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Old August 21st, 2013, 03:14 PM   #22
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Idle Air Control motor = the valve that opens and closes to adjust your idle speed.

High idle + a code for the IAC = BAD IAC.

Unplugging it just stops it from being controlled, if it's stuck open slightly, you'll see the exact behavior you describe.

-Rob
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Old August 21st, 2013, 04:29 PM   #23
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I unplugged the tps with no change.

The iac I unscrewed all the way put back in started the truck and pulled the iac off and it moved in close so I'm guessing that's not it?

And wave crusher I got ride of my 93 green chevy 350 tbi and now have a 98 red gmc vortec 350 lol
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Old August 21st, 2013, 08:06 PM   #24
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Quote:
Originally Posted by muddinman56 View Post
I unplugged the tps with no change.

The iac I unscrewed all the way put back in started the truck and pulled the iac off and it moved in close so I'm guessing that's not it?

And wave crusher I got ride of my 93 green chevy 350 tbi and now have a 98 red gmc vortec 350 lol
OHH maybe I should read then? lol 98 looks a lot like 93 right???

If you unplugged the tps and there was no change then I think you found your problem. Get a new one and make sure you don't scuff it when you put it in. If it doesn't work just take it back and say you got the wrong one. hence the not scuffing it part lol

It should be throwing a code though
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Old August 21st, 2013, 10:29 PM   #25
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My 98

I did get it scanned and auto zone but they can't tell what code is over lapping
The other it has a misfire but it does need a tune up badly but I know that's not causing the rpm problem.
They can't tell if the tps is overlapping the iac or the other way around.
But I'm not paying 60 bucks to get my truck live scanned just yet
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Old August 22nd, 2013, 08:22 AM   #26
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An engine needs air to idle at 1300 rpm.

You have an air leak someplace, either a vacuum leak someplace, a dirty / leaking throttle plate, or a bad IAC.

-Rob
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Old August 26th, 2013, 08:18 PM   #27
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You might have a misfire and an idle problem because of a bad ignition control module. When those go bad they make the motor do some weird stuff

IIRC rock auto had them for like~40$
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Old August 26th, 2013, 08:25 PM   #28
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Spider injection is probably leaking. Very common. Also, the plastic is called the plenum and it bolts to the intake. Remove thay and you will see the spider injection. Thats the only bad thing with a vortec. Or simply the throttles sticking. I assume it idles high? Start it up and look at the throttle body..
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Old August 26th, 2013, 08:28 PM   #29
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Quote:
Originally Posted by muddinman56 View Post

My 98

I did get it scanned and auto zone but they can't tell what code is over lapping
The other it has a misfire but it does need a tune up badly but I know that's not causing the rpm problem.
They can't tell if the tps is overlapping the iac or the other way around.
But I'm not paying 60 bucks to get my truck live scanned just yet
Some autozones have a little bit bigger scanner. Like one step up from the little credit card ones they use. You can read live data on the bigger one. I know the one at airport and m59 uses one. But i dknt think your near waterford.. use facebook. You would be surprised how many people have scanners or access to a friends.
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Old August 29th, 2013, 08:03 PM   #30
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Well it's not a tps,iac,maf,or map sensors and is not a vacuum leak?????
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