Resolved (HELP) 4g64 IAC - 4g63 ISC conversion

[ryan4269]

hi, I’ve followed this guide:

4G64 to 4G63t IAC Wiring Diagram

For those of you 96/97 Spyder owners trying to swap out your 4G64 throttle body for the 4g63 NA or 4g63 turbo throttle body, in order to have the 4g63 IAC work, you must rewire the 6-pin rectangle 4g64 connector to work with the 6-pin square 4g63 connector. I have attached my wiring diagram for...

www.dsmtalk.com

Though I don’t believe it’s working properly, I’m looking if anyone else has successfully done the conversion.

I believe this is my issue as my idle shoots to 2k from start, and holds it. I closed the BISS all the way shut and it lowered to 1500, but then crept back up to 2k, almost as if the IAC is backing out, or doing the opposite of what it should

 

[steve]

You're using a Turbo ECU, right?

The 4G63 ISC and the 4G64 IAC are two significantly different types of actuators, one being a stepper motor and the other a DC motor with limit switches.

If you don't have the coil wiring in the correct polarity and order the ISC won't step properly.

 

[ryan4269]

You're using a Turbo ECU, right?

The 4G63 ISC and the 4G64 IAC are two significantly different types of actuators, one being a stepper motor and the other a DC motor with limit switches.

If you don't have the coil wiring in the correct polarity and order the ISC won't step properly.

Yes I’m using a turbo ecu, 98gsx blackbox.

If I could get ahold of a pinout for the ISC pigtail I’d be able to confirm correct pins from ecu - isc.. atleast that’s all I can think of.

In the guide I posted, would you know why he’s tapping off the crank sensor power wire?

 

[steve]

If I could get ahold of a pinout for the ISC pigtail I’d be able to confirm correct pins from ecu - isc.. atleast that’s all I can think of.

Those are easy to come by.

http://www.dsmlink.com/images/forums/2GECUPinout.pdf

In the guide I posted, would you know why he’s tapping off the crank sensor power wire?

There is no good reason to split those two pins off to different power leads.

 

[ryan4269]

Those are easy to come by.

http://www.dsmlink.com/images/forums/2GECUPinout.pdf

There is no good reason to split those two pins off to different power leads.

I meant a pinout of the ISC side, connector to stepper motor. Maybe even if someone could just take a clear picture of the pigtail connected to their isc, I could then just go by matching colours with the ecu pinout.

The colour coded wires on the pigtail I have are different from what’s listed on the ecu pinout, maybe they change later down the circuit? I doubt it, maybe it’s just off a different vehicle.

Thanks for the quick communication Steve.

 

[steve]

Sorry getting sleepy in the afternoon look at page 8 in whit one.

http://www.dsmlink.com/images/forums/2GECUMFI.pdf

It tells you which pin goes where at each end and what color the wires are.

I don't have a picture of the connector handy

 

[ryan4269]

Sorry getting sleepy in the afternoon look at page 8 in whit one.

http://www.dsmlink.com/images/forums/2GECUMFI.pdf

It tells you which pin goes where at each end and what color the wires are.

I don't have a picture of the connector handy

Thanks Steve, even in the diagram it has 2 separate power leads from 2 separate sources with the cps and mfi.. weird. I’d like to know as to why. This could actually be my issue because I skipped splicing into the cps because I thought it was unnecessary.

I’ll give it a go and see what happens

 

[steve]

In that diagram you'll note that the MPI relay is feeding both ISC pins and from there the power goes towards the CPS via "D".

 

[trustedmaniac79]

I have a 98 spider gs that i turboed & am running 98 black box turbo ecu, i didn't have 2 rewire the isc. I even ran the non turbo TB before I switched 2 using a 3000gt vr4 TB, it controled either without a issue

 

[steve]

I have a 98 spider gs that i turboed & am running 98 black box turbo ecu, i didn't have 2 rewire the isc.

I defer to those that have done something but I wonder how you did so? The connectors are different, the IAC between the two are different in operation, and the wiring is different.

2G 2.4L IAC

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2G 2.0L T IAC

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Can you explain what you did?

 

[trustedmaniac79]

I'll post pics n just a few, but my ISC connector was square with 6 pins & I eventually swapped the 4g64 throttle body with a 96 3000gt vr4 throttle body. 96 vr4 ISC is supposed 2 b same as 2g turbo, but I did not have 2 rewire the ISC if using a 97-99 ecu. Just my experience

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My connector was the same as the ISC connector on the vr4 IAC, from what I read they r supposed 2 b the same as 2g turbo ISC

 

[steve]

The DSM and 3S Idle Speed Control (ISC) steppers are the same.
The FSM says that this is what the 2.4L NA IAC connector looks line and it's clearly not the same so I'm not sure what's going on.

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It wouldn't be the first error in the FSM which is why I always trust but verify.

 

[trustedmaniac79]

No this is my isc so my connector is square just like the screenshot i posted says if u have square 6 pin connector u might not have 2 rewire

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[steve]

@ryan4269 What did you car have?

 

[ryan4269]

@ryan4269 What did you car have?

Apologies for the late response,
My understanding is that the year 96 and a select bunch of unfortunate 97s have a 6 pin INLINE connector with a IAC completely different of the ISC found on turbo models AND 98+ 4g64s.

Apparently some 97s have the turbo style, but not in my case. (Or that info is just false)

I’m posting pics below so you guys can get a good reference..

Anyway, I ended up fixing my idle by adding the 2nd power wire pin to the connector. My connector was missing the pin and was plugged off.. so I had thought that it wasn’t necessary.

So in conclusion the guide I posted is accurate, besides splicing off of 2 separate power sources. (Any switched +12v power source will do)

Here are the pics..

4g64 inline connector:

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4g64 throttle body + IAC housing:

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The known 4g63t square ISC:

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