GVR-4 Galant VR4 Doesn't Idle Properly

[S_39]

Yet another bad idle post....

My Galant VR4 that I bought earlier this year (and had a plethora of issues with it that I have been solving 1-by-1) is having issues with its idling. When the engine is cold, the car doesn't even start or idle without me pumping the gas and holding it above 800rpm for a while until it starts getting warmer. When it starts to get warmer, the car can hold idle, but it surges between 1k and 2k rpm. Then, when the car is fully at operating temperature, it sits between 980-1100.

I've spent several dozens of hours searching every single forum, video, etc. on this phenomenon and I have no idea what is going on or how to fix it. Thus far I have tried:

1. Checking vacuum leaks (TIAL BOV is stuck open and hissing aggressively?)
2. Cleaning TB (spotless)
3. Adjusting BISS (car used to not even idle at all even when it was warm but now it does the afformentioned pattern)

Important things to note:

• Car is missing all emissions peripherals (normal for most modded DSMs I've seen)
• Car is missing IACV on throttle body, and was replaced with a plug of some sort
• Wiring is a mess, a bunch of stuff is missing, presumably from where it would have otherwise connected to the emissions systems
• Alternator belt is squeaky despite having JUST replaced the belt
• EDIT: AFR stays around 14.7 throughout this whole process, but when I'm out on the road, e.g. a highway, sometimes the AFR jumps between 13.4-14.7

I will add any pictures and/or videos if they are needed. I really appreciate any guidance you guys can offer.

Note: this is the first DSM I've ever owned and my first time posting on a forum like this.

 

[Vegas Smith]

Well, you're missing the idle control valve so that's kind of a problem. Replace the ISC. Do you have ECMLink?

 

[S_39]

Well, you're missing the idle control valve so that's kind of a problem. Replace the isc. Do you have ecmlink?

No unfortunately, I do not have ECMlink yet. I'm confused though; I thought ISC was just another term for the IACV?

The only thing I have yet to replace related to the throttle body is the throttle position sensor.

 

[99dsmer4g63]

Are you sure you mean your missing the IAC?

Adjusting the BISS wouldn’t do anything without an IAC and I’m not sure why you would want to remove it anyways and if the car would even idle. I think your confusing the IAC with the FIAV. If the valve your mentioning missing is in the bottom of the throttle body and 2 coolant nipples are either looped or capped on the water pipe and/or the thermostat housing it is indeed the FIAV. It increases the idle speed according to the coolant temp flowing through it.

Sounds like the they deleted the FIAV which would cause the cold start issue you are having. Seems some people do like to delete it but I have not seen the point to do so on my car and probably would leave it or repair it if ever need be.

I would suggest checking to see if it is actually the FIAV missing and replace it if you don’t like the cold start issues.
-Daniel

 

[S_39]

Are you sure you mean your missing the IAC?

Adjusting the BISS wouldn’t do anything without an IAC and I’m not sure why you would want to remove it anyways and if the car would even idle. I think your confusing the IAC with the FIAV. If the valve your mentioning missing is in the bottom of the throttle body and 2 coolant nipples are either looped or capped on the water pipe and/or the thermostat housing it is indeed the FIAV. It increases the idle speed according to the coolant temp flowing through it.

Sounds like the they deleted the FIAV which would cause the cold start issue you are having. Seems some people do like to delete it but I have not seen the point to do so on my car and probably would leave it or repair it if ever need be.

I would suggest checking to see if it is actually the FIAV missing and replace it if you don’t like the cold start issues.
-Daniel

When I said IAC I meant the palm-sized component that screws into the side of the throttle body opposite to the throttle position sensor. The previous owner is the one who removed it and I still don't know why someone would do that. The throttle body does have some lines looped and capped off; I can take a picture of the whole setup when I get home from work and attach it to the main thread for your convenience. From what I understand, the FIAV is only accessible by disconnecting the throttle body from the intake manifold, after which a lot of people I've seen block it off with a block-off plate. When I took apart the throttle body there was no block-off plate.

The only issue with me reinstalling the IAC is that even though I have the replacement piece, I don't know where to wire it in as the past owner messed with the wiring and now it looks like a rat's nest. I will attach some pictures to make this more clear.

EDIT: Apparently IAC, ISC, and FIAV are synonymous? Basically, the part missing is the valve/motor that has a plunger attached to it that screws into the throttle body opposite to the TPS location.

 

[steve]

EDIT: Apparently IAC, ISC, and FIAV are synonymous? Basically, the part missing is the valve/motor that has a plunger attached to it that screws into the throttle body opposite to the TPS location.

Not quite, ISC is the 1G name, IAC is the 2G name for the same idle speed control stepper motor. There are three types, the early 89/90 version, the metal 91+ and the replacement black plastic version.

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FIAV is the Fast Idle Air Valve that idles up the car when the coolant is cold. Again there is a 89/90 version and a later 91+
The FIAV also provides the housing for the ISC/IAC and connections for the coolant lines that open and close the FIAV bypass.

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[S_39]

Thanks Steve for clearing up any misconceptions; I currently have a replacement black plastic ISC in my possession. Attached are some images of my GVR4's engine bay:

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As you all can see, theres a whole mess of wires going to nowhere, random plugs lying around, and the vacuum lines on the TB are all looped or capped, save for the line labeled "P" that is going to some sort of black box bolted to the chassis?? I'm seriously considering pulling this wiring harness and install one pulled from a stock GVR4 donor.

Any and all help here is appreciated.

 

[Vegas Smith]

That black box is likely a MAP sensor for speed density. Look for an isc connector coming out of harness.

 

[S_39]

That black box is likely a MAP sensor for speed density. Look for an isc connector coming out of harness.

Huh, I'll look into that. As for the ISC connector, I checked around the open areas of the bay and traced all the wires back to where they could go and couldn't find anything resembling a port with 6 pins present. Does anyone have a picture of where it comes out of the firewall or fuse box and what it looks like?

 

[Vegas Smith]

I'll get you a pic late tonight or tomorrow

 

[Vegas Smith]

You should have a connector coming out of the harness around the fuel filter and injector resistor box on firewall

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[S_39]

You should have a connector coming out of the harness around the fuel filter and injector resistor box on firewall

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Thanks! I'll give it a look tonight and let you know what I find. In the case that it was indeed removed from the harness, do you think investing in a replacement harness is a good idea for me?

 

[Vegas Smith]

Thanks! I'll give it a look tonight and let you know what I find. In the case that it was indeed removed from the harness, do you think investing in a replacement harness is a good idea for me?

They probably just sliced the it off at the main harness so you can dig around where it should have been and find the wires, elongate them and buy a new isc connector at Ohm Racing. It's 6 wires and easy to fix.

 

[S_39]

They probably just sliced the it off at the main harness so you can dig around where it should have been and find the wires, elongate them and buy a new isc connector at Ohm Racing. It's 6 wires and easy to fix.

Ok I'll give it a shot, I'll let you know what I find.

 

[S_39]

Ok so I checked and it looks to me like they eradicated all trace of the wires. I did what you said and traced the main harness from the fuel rail, fuel filter, CPS, etc. and the entire assembly was taped up with electrical tape that had melted and formed some sort of goop all the way back to where the wires come from the firewall. Photos attached.

Is there a way to check at the ECU for pins going to nowhere/wires missing or does it not work like that? Thanks.

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[Vegas Smith]

Hmm, that seems unlikely but you can check the ecu connector in the middle on the ecu. On the right hand side will be a blue, black, white and yellow wire for the ISC. Check this pic:

Google Image Result for https://i0.wp.com/eatsleepdsmmag.com/wp-content/uploads/2016/02/Drawing2_Model_1_.jpg?fit=1700%2C2200&ssl=1

 

[S_39]

Hmm, that seems unlikely but you can check the ecu connector in the middle on the ecu. On the right hand side will be a blue, black, white and yellow wire for the ISC. Check this pic:

Google Image Result for https://i0.wp.com/eatsleepdsmmag.com/wp-content/uploads/2016/02/Drawing2_Model_1_.jpg?fit=1700%2C2200&ssl=1

Per usual, I am cursed with the unlikely. It appears that all 4 wires going to the ecu that control the ISC are gone (see pic).

At this point should I just get a new harness? A bunch of other wires like power steering are also gone and I plan on reinstalling that, not to mention that the wiring job was done terribly and everything is a goopy mess now because of the molten tape. P.s. huge thanks for that diagram.

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[Vegas Smith]

Hmm, not sure what to tell you. Maybe they got the harness from a 4g63 that doesn’t use an isc? No idea. You can with add an isc or get a better used harness. Adding an isc would be faster and cheaper.

 

[chrysler kid]

can you post a picture of the entire engine bay so we can see what wiring and vacuum lines and setup you have going on? Im visual and the bays and harnessed are pretty similar from 1990-1999 with some exceptions in 1990