guffey24

New install

5.3, 700R4, Jeep

motor is from a 2004, throttle body is from a 2001, performance tune, and harness from Jim's performance, got a few kinks worked out

It has idled super high 1800-2100 rpms since the first start up, throws a IAC code that reads, senses high idle

I have swapped IAC from jeep to running tahoe, both IAC's perform great on the tahoe

I have continuity through all 4 IAC wires from the computer to the harness plug, so wiring is all good

I can manually manipulate the IAC, pull it out, push it in, and I guess the computer will not change it

computer came out of a running, driving vehicle, what else am i looking for?

guffey24

blade has a stock hole, adjustment screw is all the way out

I can take the IAC out and plug the hole with my thumb and it will idle perfect between 500-700 RPm's

jimmyblue

iTrader: (11)

Are you the PCM is right for the job? Some PCMs have
the IAC driver circuitry missing.

Measure each IAC phase to GND with a DMM with the
engine running, poke through the insulation with a
needle & clip-lead. If you see less than 100mV on all
of them, the PCM isn't trying.

Ran into this on an '04 Silverado AWD doing a big cable
TB swap, had to go to an '03 Savana PCM.

guffey24

IAC driver circuitry?

Can it be added to a pcm that doesnt have it, by a tune?

Frost

iTrader: (45)

No, tuning cannot add physical circuits to a PCM

CalEditor

iTrader: (1)

What's the PCM #?

THErobertH

What insulation are you talking bout? Just anywhere along the wire? that could cause future issues, i.e. corrosion. I would back probe the connector at the connector

THErobertH

And is everything good with your fuel system? If the injectors are leaking or pulse width is too high the computer will read a rich condition increasing air in manifold and in the end raising idle.

CalEditor

iTrader: (1)

PCM's with IAC driversGreen is good Red is not

Frost

iTrader: (45)

the 896 and 411 PCMs have the driver, are fairly common, and will run that engine well also..

guffey24

will check the numbers tommorrow, Jim has flashed and tuned another computer for me, should be here tommorrow

guffey24

I have good fuel pressure, new corvette regulator, WIX, with a return line

not sure if the injectors are leaking, motor didnt have but 38,000 miles on it from the wrecked vehicle

how do you check pulse width?

I had a lean and rich code at first, but o2 sensors were backwards

THErobertH

I don't really see a injectors with 38k mi. on them leaking. You could use a DSO, such as a picoscope, but doubt you would want to pay full price for one.

Frost

iTrader: (45)

had a 42 hang open after about 4 hours of use...

guffey24

New computer didnt change a thing, still high idle

I put the old computer back in, pulled the IAC out, manually pulled it completely out where the IAC seperated the plunger from the spring, put it back together enough to where it should be at idle, reinstalled the IAC, and it sat there and idled perfect

The computer is not controlling the IAC

guffey24

computer is 6247

CalEditor

iTrader: (1)

What year is it out of?

Frost

iTrader: (45)

that's not a complete/valid part number

CalEditor

iTrader: (1)

1999 to 2002 all PCM's support IAC
2003+
SERV. NO. - HWD NO.
12576106 - 12570558 - 2003 G-VAN, LM7, IAC DRIVERS. C1500 LM7
12586243 - 12583659 - 2004 GTO LS1, IAC DRIVERS
12589462 - 12589161 - 2005 G-VAN, LQ4, IAC DRIVERS
12602801 - 12589161 - 2006 - 2007 Express, Drive by Wire, (has IAC drivers)


2004
Silverado PCM, DOES NOT WORK with cable throttle:
Serv. No. 12586242
Hwd. No. 12593660

2005 & 2006
Silverado PCM, DOES NOT WORK with cable throttle:
Serv. No. 12589463
Hwd. No. 12589162

guffey24

well this makes some since, my original computer has the IAC drivers

my computer numbers
serv. No. 12586242
hwd. no. 12583660

Test computer I got yesterday, doesnt have IAC drivers

serv. no. 12589463
hdw. no. 12589162