# Throttle Body / IAC question - MegaSquirt



## Tikigod_III (Oct 11, 2004)

Hi everyone,
I'm at the beginning stages of a MegaSquirt installation and I'm trying to figure something out.
This question specifically pertains to an OBDII 2.0L 8v (ABA).
In this application, there is no such thing as the Idle Air Control Valve, and instead that function is integrated into the throttle body itself. So, there is a 7-pin connector on the TB instead of a 3-pin.
Does anyone have experience using this TB with MegaSquirt? I'm using the V3/MS-II setup, which has provisions for an IAC Stepper motor, but I don't know quite how that would operate with this TB, with the 'IAC' actually being to adjust the throttle plate.
---
I'm going to pull the TB at way too ass early in the morning tomorrow and take it into the electronics lab here at school and play with it. Correct me if I am wrong, but, I figure that if the IAC function can adjust the angle of the throttle plate, without changing the value the TPS is reading then everything should work fine as long as I can figure out the wiring.
Please, drop any insight you may have on the issue.
Matt


----------



## bunnyslayer (Nov 2, 2006)

*Re: Throttle Body / IAC question - MegaSquirt (Tikigod_III)*

I have never played with this type of throttle body.. But if it’s a stepper motor iac that adjusts the angle of the throttle plate you would want the tps value to change as well that way m/s will adjust the fuelling/timing for the higher idle rpm


_Modified by bunnyslayer at 10:32 PM 1-30-2008_


----------



## need_a_VR6 (May 19, 1999)

*Re: Throttle Body / IAC question - MegaSquirt (Tikigod_III)*

The OBD2 IAC isn't a stepper, it's a PWM controlled DC motor. I believe the MS2 Extra code can handle it if the normal base MS2 can't.


----------



## sdezego (Apr 23, 2004)

*Re: Throttle Body / IAC question - MegaSquirt (Tikigod_III)*

I know there are people running them, but not using them for idle control.
There is a trick though that you can use for a fast idle. If you energize pin1 with 12v (3Amps)
I have never tried this personally, but know there is one or two people that have done it.

Throttle Valve control unit
(without cruise control)
(06A 133 063 G)
1. actuator +12V/3A (idle control)
2. actuator GND (idle control)
3. throttle closed = pin 7 / open = ∞
4. GND
5. TPS (0.6V closed / 4.3V full)
6. Not connected
7. +5V
8. Not needed (TPS with smaller range)


----------



## need_a_VR6 (May 19, 1999)

*Re: Throttle Body / IAC question - MegaSquirt (sdezego)*

I know that to use that TB on OBD1 you have to swap pin 7/4 so the TPS count goes up with opening throttle as well.


----------



## Tikigod_III (Oct 11, 2004)

*Re: Throttle Body / IAC question - MegaSquirt (need_a_VR6)*


_Quote, originally posted by *need_a_VR6* »_The OBD2 IAC isn't a stepper, it's a PWM controlled DC motor.

Yea, I caught that last night while I was researching and making my head explode.
Looking through the MS instructions, it would appear that setting up for a PWM IAC is a giant pain in the balls as you need to put in componants with higher power handling capability. I'm not quite ready to tackle that yet, so I might try to rig it as an FIdle setup instead.

_Quote, originally posted by *sdezego* »_
Throttle Valve control unit
(without cruise control)
(06A 133 063 G)
1. actuator +12V/3A (idle control)
2. actuator GND (idle control)
3. throttle closed = pin 7 / open = �‡
4. GND
5. TPS (0.6V closed / 4.3V full)
6. Not connected
7. +5V
8. Not needed (TPS with smaller range)


The Bentley wiring diagram (pg. 97-265, J338) shows pin 7 as GND and pin 4 as +5V. So there may be more than one configuration for that connector?
I'm glad to know what pin 8 is finally, I almost blew my brains out trying to find out last night.
I'll test the 12v/3A to pin 1 for FIdle in the next few days at school and let you know how it works.
Thanks for all the help guys.

_Modified by Tikigod_III at 11:53 AM 1-31-2008_


_Modified by Tikigod_III at 12:09 PM 1-31-2008_


----------



## need_a_VR6 (May 19, 1999)

*Re: Throttle Body / IAC question - MegaSquirt (Tikigod_III)*

All you need to do is change one transistor, it's not that hard!
I'd have to double check on my car but I had to reverse the tps wires on my car from the way the colors were, the brown wire needed +5v, and the red/white I needed to ground to work on an OBD1 VR6 with 'normal' style tps. I'm not sure if the above already takes that into account.


----------



## Tikigod_III (Oct 11, 2004)

*Re: Throttle Body / IAC question - MegaSquirt (need_a_VR6)*

One last update on this saga for anyone who may find this thread via Search, and also because I finally satisfied my curiousity.
In regard to pin 8 and as to why there are two potentiometers in the throttle body: Motronic uses the potentiometer on Pin 8 to monitor the position of the PWM IAC motor. That way it can differentiate between movement in the throttle plate due to IAC and movement due to driver input so that it doesn't start infinite adjustment loops.
I found that information in Section 24b of the Bentley and it's just briefly mentioned.
For super cool MS kids, the FIdle business with 12v/3Amps does work, as does just a regular PWM idle control. For my application (track car) I could give a crap about idle, so it's easier to do an FIdle setup.


----------



## Flipdriver80 (Jul 17, 2004)

what i did with my car is run an OBD1 throttle body with the 3 pin connector and ditch the IAC setup. works great. idle jumps a few RPM's once in a while but really not a big deal.


----------

