4.8 LS swap IAC not moving

Hi guys,

I am working on a 56 cadillac with a 4.8 4l80e combo. The engine is stock except for a holley 300-137 single plane intake and matching 112-588 4 bbl throttle body. the car will start and idle but then dies. The IAC is not responding but I can control it with the special functions in the scanner. the car is also running quite rich (eye watering). the car will also stumble quite bad and die when it goes into gear. the engine was running great when pulled from the donor and the stock tune is being used (with vats deleted and a 2 bar SD conversion). i'm hoping someone can point me in the right direction to get this thing to run properly. current tune file and a logs attatched.

Attachment 120418
Attachment 120419

If i remember right you might need to swap some wires on the IAC? I remember having a similar issue with one a couple years ago.. Pretty sure we just put a holley ECU on the car later tho.. Does it have a GM IAC or does it have the Holley IAC?

Found this on another forum from one of the tuners.

"Holley uses the Chrysler IAC on those TBs become they have a larger diameter plunger, thus they flow more. I believe they function the same as the LS IACs, but the plugs are different, and also the pinout is different. I would consult the different Holley wiring diagrams for details."



From Holley Instructions..


"Idle Air Control Motor (IAC) ? This is a Chrysler style and must be pinned as below.
A ? A Low
B ? B High
C ? B Low
D ? A High
Connector PN ? 12162188
Pin ? 12124076 (20-22ga)"

Its idling higher than commanded so its trying to pull a ton of timing. That puts you around -10* at idle.

Get the IAC figured out and it should help stabilize idle.

The MAF isn't failed correctly either for speed density. Set the MAF fail high to 0hz and all 3 MAF dtc's to MIL on first error with the SES box unchecked.

Are you using the stock injectors in that intake as well as stock fuel pressure settings?

Quote:

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Originally Posted by RDF1

If i remember right you might need to swap some wires on the IAC? I remember having a similar issue with one a couple years ago.. Pretty sure we just put a holley ECU on the car later tho.. Does it have a GM IAC or does it have the Holley IAC?

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Quote:

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Originally Posted by RDF1

Found this on another forum from one of the tuners.

"Holley uses the Chrysler IAC on those TBs become they have a larger diameter plunger, thus they flow more. I believe they function the same as the LS IACs, but the plugs are different, and also the pinout is different. I would consult the different Holley wiring diagrams for details."



From Holley Instructions..


"Idle Air Control Motor (IAC) ? This is a Chrysler style and must be pinned as below.
A ? A Low
B ? B High
C ? B Low
D ? A High
Connector PN ? 12162188
Pin ? 12124076 (20-22ga)"

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Quote:

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Originally Posted by RDF1

Its idling higher than commanded so its trying to pull a ton of timing. That puts you around -10* at idle.

Get the IAC figured out and it should help stabilize idle.

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I do have the wires swapped but I?ll triple check they are pinned correctly

Quote:

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Originally Posted by 5FDP

The MAF isn't failed correctly either for speed density. Set the MAF fail high to 0hz and all 3 MAF dtc's to MIL on first error with the SES box unchecked.

Are you using the stock injectors in that intake as well as stock fuel pressure settings?

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Thanks for pointing that out, I had changed that in the subsequent tune but put this one back in and forgot I hadn?t changed it!

I am using stock injectors at 58.5psi

These are the only P59 PCMs that have IAC drivers. Service number and hardware number must match exactly.

2007
Service # - 12602801
Hardware # - 12589161

2006 - 2005
Service # - 12589462
Hardware # 12589161

2004
Service # - 12586243
Hardware # - 12583659

2003
Service # - 12576106
Hardware # - 12570558

12200411 – xxxxxxxx – 2002 F-Body, Corvette, S10, IAC DRIVERS INSTALLED
09354896 – xxxxxxxx – IAC DRIVERS INSTALLED.
12576106 – 12570558 – 2003 G-VAN, LM7, IAC DRIVERS INSTALLED. ALSO C-TRUCK LM7
12582605 – 12580786 – 2003 C-MPV, L59 NOT INSTALLED
12586242 – 12583660 – 2004 C/K-TRUCK, LM7 NOT INSTALLED
12586243 – 12583659 – 2004 GTO LS1, IAC DRIVERS INSTALLED
12589463 – 12589162 – 2005 C/K-TRUCK/MPV, LM7, LQ4 NOT INSTALLED
12589462 – 12589161 – 2005 G-VAN, LQ4, IAC DRIVERS INSTALLED
12589463 – 12589162 – 2006 C-PICKUP, LM7 NOT INSTALLED
12602802 – 12589162 – 2006 C-PICKUP, L59 NOT INSTALLED
12602801 – 12589161 – 2006 – 2007 Express, Drive by Wire, IAC DRIVERS INSTALLED

Quote:

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Originally Posted by TheMechanic

These are the only P59 PCMs that have IAC drivers. Service number and hardware number must match exactly.

2007
Service # - 12602801
Hardware # - 12589161

2006 - 2005
Service # - 12589462
Hardware # 12589161

2004
Service # - 12586243
Hardware # - 12583659

2003
Service # - 12576106
Hardware # - 12570558

12200411 – xxxxxxxx – 2002 F-Body, Corvette, S10, IAC DRIVERS INSTALLED
09354896 – xxxxxxxx – IAC DRIVERS INSTALLED.
12576106 – 12570558 – 2003 G-VAN, LM7, IAC DRIVERS INSTALLED. ALSO C-TRUCK LM7
12582605 – 12580786 – 2003 C-MPV, L59 NOT INSTALLED
12586242 – 12583660 – 2004 C/K-TRUCK, LM7 NOT INSTALLED
12586243 – 12583659 – 2004 GTO LS1, IAC DRIVERS INSTALLED
12589463 – 12589162 – 2005 C/K-TRUCK/MPV, LM7, LQ4 NOT INSTALLED
12589462 – 12589161 – 2005 G-VAN, LQ4, IAC DRIVERS INSTALLED
12589463 – 12589162 – 2006 C-PICKUP, LM7 NOT INSTALLED
12602802 – 12589162 – 2006 C-PICKUP, L59 NOT INSTALLED
12602801 – 12589161 – 2006 – 2007 Express, Drive by Wire, IAC DRIVERS INSTALLED

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The ecm came out of a drive by cable van and i can manually move the iac using the scanner special functions. I?ll double check the ecm to make sure but I?m fairly certain it has drivers

So to update, I have verified the wiring to the iac is correct and the ecm definitely has the iac drivers.

I can control the iac with the scanner only when the key is on but the engine is off. Is there any way the coils could be causing interference? They have been relocated and are now right next to the harness.