Stripped IAC Worm Gear?
Thread Starter
Drifting
Joined: Jul 2014
Posts: 1,426
Likes: 46
From: Lynchburg, VA
Stripped IAC Worm Gear?
As some of you know, I'm having problems with my idle being too high. Someone suggested a stripped worm gear on the IAC, and I suspect that's the case. When I jumped ALDL pins A and B to get the IAC to extend so I could set the base idle, I noticed the IAC was making a rattling noise and the connector was heavily vibrating. I can't find a picture of what the pintle looks like, but I'm assuming it's the "wall" sticking up out of the bottom of the TB several inches back? If so, I can see that sticking up ~1/3". When I turn the engine to "on" with pins A and B jumped it doesn't move at all. I'm assuming this is because the gear is stripped?
If so, does anyone have a link to a replacement gear? I'm looking, and all I've found is this: http://www.ecklerscorvette.com/corve...1989-1994.html. I'd rather not spend $115 plus shipping to fix a stripped gear.
EDIT: Okay, I found one for $23. Guess this isn't as big of a deal as I thought. http://www.ebay.com/itm/Idle-Air-Control-Valve-IAC-/271520794748?pt=Motors_Car_Truck_Parts_Accessories&fits=Year%3A1990%7CModel%3ACorvette&hash=item3f37e6887c&vxp=mtrI'd still like to confirm that the gear is stripped though.
My car is a 1990.
If so, does anyone have a link to a replacement gear? I'm looking, and all I've found is this: http://www.ecklerscorvette.com/corve...1989-1994.html. I'd rather not spend $115 plus shipping to fix a stripped gear.
EDIT: Okay, I found one for $23. Guess this isn't as big of a deal as I thought. http://www.ebay.com/itm/Idle-Air-Control-Valve-IAC-/271520794748?pt=Motors_Car_Truck_Parts_Accessories&fits=Year%3A1990%7CModel%3ACorvette&hash=item3f37e6887c&vxp=mtrI'd still like to confirm that the gear is stripped though.
My car is a 1990.
Last edited by C4ProjectCar; Aug 25, 2014 at 04:13 PM.
Le Mans Master
Joined: Aug 2007
Posts: 8,735
Likes: 412
From: WV
Here is one I found on ebay, it's a Delphi which was one of GMs suppliers for OE parts....I have used Delphi parts many times...WW
Again this has free shipping...
http://www.ebay.com/itm/Delphi-CV10029-Idle-Air-Control-Motor-/271584989005?pt=Motors_Car_Truck_Parts_Accessories&fits=Year%3A1989%7CModel%3ACorvette&hash=item3f3bba0f4d&vxp=mtr#ht_1811wt_1206
Again this has free shipping...
http://www.ebay.com/itm/Delphi-CV10029-Idle-Air-Control-Motor-/271584989005?pt=Motors_Car_Truck_Parts_Accessories&fits=Year%3A1989%7CModel%3ACorvette&hash=item3f3bba0f4d&vxp=mtr#ht_1811wt_1206
Last edited by WW7; Aug 28, 2014 at 06:22 AM.
Thread Starter
Drifting
Joined: Jul 2014
Posts: 1,426
Likes: 46
From: Lynchburg, VA
Pat, here is one I found on ebay, it's a Delphi which was one of GMs suppliers for OE parts....I have used Delphi parts many times...WW
Again this has free shipping...
Delphi CV10029 Idle Air Control Motor | eBay
Again this has free shipping...
Delphi CV10029 Idle Air Control Motor | eBay
I found one from AC Delco, but it was a bit more.
Le Mans Master
Joined: Aug 2007
Posts: 8,735
Likes: 412
From: WV
Sorry I thought you were someone else..
...The one you found will probably work, but it says it's a generic brand..
...It's up to you but I feel better buying from a company that I've heard of....
.. It says it has a warrenty but how long??? 30 days ......30 minutes...
....WW
...The one you found will probably work, but it says it's a generic brand.....It's up to you but I feel better buying from a company that I've heard of...... It says it has a warrenty but how long??? 30 days ......30 minutes.......WW
Le Mans Master
Joined: Aug 2007
Posts: 8,735
Likes: 412
From: WV
I don't know if the ac delco is better then the Delphi , but I know either one of them is better then the one for $23.00.......I agree with checking to make sure the old IAC is bad before buying a new one, these old cars have enough parts go bad without replacing stuff that still works.....WW
...I agree with checking to make sure the old IAC is bad before buying a new one, these old cars have enough parts go bad without replacing stuff that still works.....WW
Thread Starter
Drifting
Joined: Jul 2014
Posts: 1,426
Likes: 46
From: Lynchburg, VA
It has a 12 month warranty, which is just as long as the AC Delco unit.
Thread Starter
Drifting
Joined: Jul 2014
Posts: 1,426
Likes: 46
From: Lynchburg, VA
I don't know if the ac delco is better then the Delphi , but I know either one of them is better then the one for $23.00.......I agree with checking to make sure the old IAC is bad before buying a new one, these old cars have enough parts go bad without replacing stuff that still works.....WW
...I agree with checking to make sure the old IAC is bad before buying a new one, these old cars have enough parts go bad without replacing stuff that still works.....WWSince the "wall" AKA the pintle in the throttle body doesn't raise when I turn the key to "on" with ALDL pins A and B jumped, yet I can hear the motor running, I'm pretty sure it's bad. Somebody please correct me if I'm wrong.
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Thread Starter
Drifting
Joined: Jul 2014
Posts: 1,426
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From: Lynchburg, VA
Don't know what year is your Vette but here is a link to an '85-'88 Vette IAC at Rock Auto for ~$80, along with a pic of the assy.
Burning Brakes
Joined: Jul 2013
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From: Granite City Illinois
Thread Starter
Drifting
Joined: Jul 2014
Posts: 1,426
Likes: 46
From: Lynchburg, VA
Now I just need to confirm it's broken. I'm pretty sure it is, but I'd like assurance.
Race Director
Joined: Apr 2002
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From: Anaheim CA
When I jumped ALDL pins A and B to get the IAC to extend so I could set the base idle, I noticed the IAC was making a rattling noise and the connector was heavily vibrating. I can't find a picture of what the pintle looks like, but I'm assuming it's the "wall" sticking up out of the bottom of the TB several inches back?
The pintle is inside the throttle body. You cannot see it unless you take the IAC out. The IAC is a stepper motor. It has a threaded shaft and turning the motor makes the shaft move in and out. There is a special integrated circuit (stepper motor driver) inside the ECM that handles the movement of the IAC.
Le Mans Master
Joined: Aug 2007
Posts: 8,735
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From: WV
To clean it you need to remove the throttle body, then unscrew the IAC. You then have to remove the screws from the bottom plate to get to the air channels that feed the IAC..Brake cleaner and an old toothbrush will get the job done on the channels...There will probably be buildup on the pintle tip also, you can just shoot the brake cleaner on the tip to clean it , just be careful not to break the pintle..Reassemble all back together...WW
Burning Brakes
Joined: Mar 2013
Posts: 1,131
Likes: 5
From: Illinois/Wisconsin Line
Dude Your IAC or air-bypass valve is a Stepper-motor with I think a worm gear and has maybe 125 different possible commandable steps and usually fails at its last commanded step and triggers a check engine light. All it does is, it throws air passed the throttle plate to vary Idle without having to crack the butterfly manually thru a coolant temp for start up and then under certain engine load up conditions. Once u move the throttle/butterfly thur the TPS. The IAC is done/not used/turned off/not needed.
Any problems with that, commands that u, remove the throttle body assy and do the usual complete soak and clean of the throttle body and its passages. While thats being done you check the resistance of the IAC Itself { with it off } or just jump it like you said and see if it does move or not.
If its moving smoothly, clean everything and put it back together, if not replace the IAC and set base Idle position and it will do its thing and hunt and learn and You'll be good
Any problems with that, commands that u, remove the throttle body assy and do the usual complete soak and clean of the throttle body and its passages. While thats being done you check the resistance of the IAC Itself { with it off } or just jump it like you said and see if it does move or not.
If its moving smoothly, clean everything and put it back together, if not replace the IAC and set base Idle position and it will do its thing and hunt and learn and You'll be good
Thread Starter
Drifting
Joined: Jul 2014
Posts: 1,426
Likes: 46
From: Lynchburg, VA
When you jump pins A & B the ECM starts pulsing the IAC to extend the pintle. It will continue to do that as long as you have A & B connected together. That's why it vibrates and makes a noise.
The pintle is inside the throttle body. You cannot see it unless you take the IAC out. The IAC is a stepper motor. It has a threaded shaft and turning the motor makes the shaft move in and out. There is a special integrated circuit (stepper motor driver) inside the ECM that handles the movement of the IAC.
The pintle is inside the throttle body. You cannot see it unless you take the IAC out. The IAC is a stepper motor. It has a threaded shaft and turning the motor makes the shaft move in and out. There is a special integrated circuit (stepper motor driver) inside the ECM that handles the movement of the IAC.
I finally found a video explaining how the IAC works. It's not at all like I thought.
For anyone that might use this thread as a resource in the future, here's the video:
Thread Starter
Drifting
Joined: Jul 2014
Posts: 1,426
Likes: 46
From: Lynchburg, VA
Dude Your IAC or air-bypass valve is a Stepper-motor with I think a worm gear and has maybe 125 different possible commandable steps and usually fails at its last commanded step and triggers a check engine light. All it does is, it throws air passed the throttle plate to vary Idle without having to crack the butterfly manually thru a coolant temp for start up and then under certain engine load up conditions. Once u move the throttle/butterfly thur the TPS. The IAC is done/not used/turned off/not needed.
Any problems with that, commands that u, remove the throttle body assy and do the usual complete soak and clean of the throttle body and its passages. While thats being done you check the resistance of the IAC Itself { with it off } or just jump it like you said and see if it does move or not.
If its moving smoothly, clean everything and put it back together, if not replace the IAC and set base Idle position and it will do its thing and hunt and learn and You'll be good
Any problems with that, commands that u, remove the throttle body assy and do the usual complete soak and clean of the throttle body and its passages. While thats being done you check the resistance of the IAC Itself { with it off } or just jump it like you said and see if it does move or not.
If its moving smoothly, clean everything and put it back together, if not replace the IAC and set base Idle position and it will do its thing and hunt and learn and You'll be good
Thread Starter
Drifting
Joined: Jul 2014
Posts: 1,426
Likes: 46
From: Lynchburg, VA
To clean it you need to remove the throttle body, then unscrew the IAC. You then have to remove the screws from the bottom plate to get to the air channels that feed the IAC..Brake cleaner and an old toothbrush will get the job done on the channels...There will probably be buildup on the pintle tip also, you can just shoot the brake cleaner on the tip to clean it , just be careful not to break the pintle..Reassemble all back together...WW
Burning Brakes
Joined: Mar 2013
Posts: 1,131
Likes: 5
From: Illinois/Wisconsin Line
Not sure on the exact numbers but in my experience you have resistance or not. I used to just go to the parts counter at GM and get whatever they had to soak the tb in for an hr or 2 and scrub it and then blow it off with compressed air. The main thing you want to get is the crud off the throttle body's space in between the throttle body and the butterfly. Lowers O2 Cross counts and off Idle stumbles
Like this
Like this
Last edited by cudamax; Aug 26, 2014 at 03:33 PM.