IAC Bench Test
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From: Cocoa, Florida
Car: 2006 Ford F-250 Diesel
IAC Bench Test
Fighting a High Idle Issue, idles @ 1200 RPM. So I smoke tested intake thru a Vacuum Port, no indications of leak. Performed the IAC Reset procedure, now idles @ 1500 RPM. Reset TPS to 0.55vdc, no change. Bad IAC???
Pulled the IAC out and set up on bench with a 5vdc pulse, IAC Jerked once, then nothing. Tried shifting polarity, no motion, tried both motor winding, no motion. Each motor winding reads 58 ohms. IAC is open @ 29mm (spec is 28mm)
Not a big fan of the Parts Shotgun Effect. Too much time at sea without a parts counter to buy parts.
Before I pull the trigger on a new IAC, any ideas?
Pulled the IAC out and set up on bench with a 5vdc pulse, IAC Jerked once, then nothing. Tried shifting polarity, no motion, tried both motor winding, no motion. Each motor winding reads 58 ohms. IAC is open @ 29mm (spec is 28mm)
Not a big fan of the Parts Shotgun Effect. Too much time at sea without a parts counter to buy parts.
Before I pull the trigger on a new IAC, any ideas?
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From: Chasing Electrons
Car: check
Engine: check
Transmission: check
Re: IAC Bench Test
The IAC is a bi-polar stepper motor. It runs from 12 volts. There are some hobbyist circuits out there to run one. Note that bi-polar means that there are two coils. Of which the polarity goes forward and reversed, dependent upon whether to step in or step out. Along with at which point the stepping is.
Do need electronics to run an IAC. Way back I built a box to do this. It does come in handy. But for the most part is hardly used.
The first part of the IAC set up (minimum idle air) procedure continuously steps the IAC closed. Don't do this with the IAC out of the TB.
RBob.
Do need electronics to run an IAC. Way back I built a box to do this. It does come in handy. But for the most part is hardly used.
The first part of the IAC set up (minimum idle air) procedure continuously steps the IAC closed. Don't do this with the IAC out of the TB.
RBob.
Last edited by RBob; Feb 25, 2023 at 05:21 PM. Reason: speelling, or some such thing...
Thread Starter
Junior Member
Joined: Feb 2020
Posts: 40
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From: Cocoa, Florida
Car: 2006 Ford F-250 Diesel
Re: IAC Bench Test
Hmm, 12 volts you say? That could explain the no movement. I will try to pulse 12vdc on the coils. If there is movement, I will report back. I am used to 5vdc on Servo Motors (time in the navy as an ET). Once I prove the IAC is good, I will pulse to achieve 28mm and reinstall. More in the AM. Thanks RBob. The service manual provides no info on this. MUST USE TECH 1 AND A GM TRAINED SERVICE TECH. ;-)
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Junior Member
Joined: Feb 2020
Posts: 40
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From: Cocoa, Florida
Car: 2006 Ford F-250 Diesel
Re: IAC Bench Test
Update. Installed IAC back in the Throttle Body Lower Plate. Applied 12vdc, no motion. Tried various configurations for the 12vdc supply, nothing . Need a new IAC
While I was at it, pulled the MAP Sensor to verify operation using 5vdc. Pulled 20" of vacuum, voltage dropped from 4.8vdc to 0.950 vdc. Watched the voltage slowly rise over a 45 second period while holding 20 " of vacuum from 0.950 to 1.030vdc. Hmmmm, going to replace the MAP as well.
Nothing to complain about, had the car for 18 years with no issues. Time catches up to all of us.
While I was at it, pulled the MAP Sensor to verify operation using 5vdc. Pulled 20" of vacuum, voltage dropped from 4.8vdc to 0.950 vdc. Watched the voltage slowly rise over a 45 second period while holding 20 " of vacuum from 0.950 to 1.030vdc. Hmmmm, going to replace the MAP as well.
Nothing to complain about, had the car for 18 years with no issues. Time catches up to all of us.
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Joined: May 2005
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From: Newark, DE USA
Car: 88 IROC-Z T-Top car with Bose
Engine: L98 5.7
Transmission: 700R4
Axle/Gears: 9 Bolt with 3.27's
Re: IAC Bench Test
Hello there,
Did you happen to fix this issue? Have a friend fighting a similar problem. All help is appreciated!
Did you happen to fix this issue? Have a friend fighting a similar problem. All help is appreciated!
Update. Installed IAC back in the Throttle Body Lower Plate. Applied 12vdc, no motion. Tried various configurations for the 12vdc supply, nothing . Need a new IAC
While I was at it, pulled the MAP Sensor to verify operation using 5vdc. Pulled 20" of vacuum, voltage dropped from 4.8vdc to 0.950 vdc. Watched the voltage slowly rise over a 45 second period while holding 20 " of vacuum from 0.950 to 1.030vdc. Hmmmm, going to replace the MAP as well.
Nothing to complain about, had the car for 18 years with no issues. Time catches up to all of us.
While I was at it, pulled the MAP Sensor to verify operation using 5vdc. Pulled 20" of vacuum, voltage dropped from 4.8vdc to 0.950 vdc. Watched the voltage slowly rise over a 45 second period while holding 20 " of vacuum from 0.950 to 1.030vdc. Hmmmm, going to replace the MAP as well.
Nothing to complain about, had the car for 18 years with no issues. Time catches up to all of us.
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Joined: Feb 2020
Posts: 40
Likes: 2
From: Cocoa, Florida
Car: 2006 Ford F-250 Diesel
Re: IAC Bench Test
Rumblin70SS,
No sir, still having issues getting the engine started. I am troubleshooting a bad ECM as I can't even get a NOID Light to indicate an injector pulse. New(refurbished) ECM due Wednsday(?). I will report back.
No sir, still having issues getting the engine started. I am troubleshooting a bad ECM as I can't even get a NOID Light to indicate an injector pulse. New(refurbished) ECM due Wednsday(?). I will report back.
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Member
Joined: May 2005
Posts: 375
Likes: 0
From: Newark, DE USA
Car: 88 IROC-Z T-Top car with Bose
Engine: L98 5.7
Transmission: 700R4
Axle/Gears: 9 Bolt with 3.27's
Re: IAC Bench Test
Ugh thank you, look forward to hearing back and good luck!
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