ECMlink 98 GST Idle tuning

Zanaqqq · Jul 20, 2026

Been awhile since I posted on here..

So I’m having some issues getting the car to reach its target idle. The airflowperrev is around .28 to .35 at idle. My wideband will read it’s running lean when it’s near target idle but when I add a little more fuel to get that 14:7 it raises the idle too. I’m wondering what issue this could be and what’s causing it.

It also has a rev hang and sits about 1500 before coming back down to 1100-1200. My target idle is set to 750 on this log I’ve uploaded below.

The one thing I saw was my ISC position was way to high but the airflow read okay.

I’ll take any ideas or things to check.

pauleyman · Jul 20, 2026

Why are you locked in open loop? Whats the reasoning behind the MAF comp changes?
Please update your profile. Obviously you have ECMLink but as the settings suggest it's a stock MAF? What size injectors and what kind?

Zanaqqq · Jul 20, 2026

pauleyman said:
Why are you locked in open loop? Whats the reasoning behind the MAF comp changes?
Please update your profile. Obviously you have ECMLink but as the settings suggest it's a stock MAF? What size injectors and what kind?

I was unaware I had the car locked in open loop, and changing the MAF comp sliders seemed to help the idle go a little lower. Car is on stock MAF, and 1200cc injectors unknown brand they have no labeling on them. I am on E85 as well.

DSMPT · Jul 21, 2026

Zanaqqq said:
It also has a rev hang and sits about 1500 before coming back down to 1100-1200. My target idle is set to 750 on this log I’ve uploaded below.

Do you happen to use a 1g CAS? If so, have you confirmed that the base ignition timing is set properly? Maybe it's too advanced?
And if the idle RPM doesn't lower below a certain RPM by bottoming out the BISS, I would also suspect that the throttle body (Cable, Fixed SAS, TPS and BISS) is not adjusted properly or/and there is vacuum leak.

dwb · Jul 21, 2026

Your ISCPosition isn't moving. I'd start by figuring out why.

Zanaqqq · Jul 21, 2026

DSMPT said:
Do you happen to use a 1g CAS? If so, have you confirmed that the base ignition timing is set properly? Maybe it's too advanced?
And if the idle RPM doesn't lower below a certain RPM by bottoming out the BISS, I would also suspect that the throttle body (Cable, Fixed SAS, TPS and BISS) is not adjusted properly or/and there is vacuum leak.

I do have a 1g cas and base timing is set correctly. I’m gonna take apart my throttle body later this week and check everything. Then do leak test after

Zanaqqq · Jul 21, 2026

dwb said:
Your ISCPosition isn't moving. I'd start by figuring out why.

What could cause that?

dwb · Jul 21, 2026

Read through this:

idlesurge [ECMTuning - wiki]

www.ecmtuning.com

Pay attention to the blown driver chip page too:

driver01 [ECMTuning - wiki]

www.ecmtuning.com

If you inspect the ECU and aren't certain if it's damaged (look for green corrosion and/or burnt spots), feel free to post a clear picture of the board here.

Zanaqqq · Jul 21, 2026

dwb said:
Read through this:
idlesurge [ECMTuning - wiki]
www.ecmtuning.com
Pay attention to the blown driver chip page too:
driver01 [ECMTuning - wiki]
www.ecmtuning.com
If you inspect the ECU and aren't certain if it's damaged (look for green corrosion and/or burnt spots), feel free to post a clear picture of the board here.

You must be logged in to view this image or video.

dwb · Jul 21, 2026

Looks ok to me.

Zanaqqq · Jul 21, 2026

dwb said:
Your ISCPosition isn't moving. I'd start by figuring out why.

My isc position does fluctuate while idling. Just not in that log for some reason

dwb · Jul 21, 2026

Zanaqqq said:
My isc position does fluctuate while idling. Just not in that log for some reason

Do you see RPM change associated with it?

Zanaqqq · Jul 21, 2026

dwb said:
Do you see RPM change associated with it?

It did get lower and the isc number dropped. Very little rpm change. I just got done putting in my fiav bypass plate so I’ll run a leak test tomorrow

DSMPT · Jul 21, 2026

Zanaqqq said:
I do have a 1g cas and base timing is set correctly

When did you do? Did you do that by yourself?

Zanaqqq said:
I’m gonna take apart my throttle body later this week and check everything. Then do leak test after

Which throttle body do you have? Have you or the previous owners ever changed the position of fixed SAS?

Zanaqqq · Jul 21, 2026

DSMPT said:
When did you do? Did you do that by yourself?

Which throttle body do you have? Have you or the previous owners ever changed the position of fixed SAS?

I just set the base timing. The cas and 6 bolt swap was already done when I bought it.

I think it’s a 1g throttle body. And I don’t think anyone has touched that.

DSMPT · Jul 21, 2026

Zanaqqq said:
I just set the base timing. The cas and 6 bolt swap was already done when I bought it.

I think it’s a 1g throttle body. And I don’t think anyone has touched that.

By a timing light?

Zanaqqq said:
I think it’s a 1g throttle body. And I don’t think anyone has touched that.

Please upload a pic. If it's a 1g throttle body, the fixed SAS is easily touched, so there is more chance that the throttle plate is open more than it should, that would cause high idle.

Zanaqqq · Jul 21, 2026

DSMPT said:
By a timing light?

Please upload a pic. If it's a 1g throttle body, the fixed SAS is easily touched, so there is more chance that the throttle plate is open more than it should, that would cause high idle.

Yes I bought a new timing light to do it and used the factory crank marks till it was 5 degrees.

I’ll get a pic I’ll upload within the next 10 or so min

Zanaqqq · Jul 21, 2026

DSMPT said:
By a timing light?

Please upload a pic. If it's a 1g throttle body, the fixed SAS is easily touched, so there is more chance that the throttle plate is open more than it should, that would cause high idle.

You must be logged in to view this image or video.

DSMPT · Jul 21, 2026

Zanaqqq said:
You must be logged in to view this image or video.

Have you ever set the fixed SAS position properly before? The fixed SAS is with the IPS on 1g throttle body.
In case if the idle engine speed doesn't go down below a certain point by bottoming out the BISS, but if it does by loosing the fixed SAS (IPS), then most likely you would need to readjust the position of the fixed SAS and BISS. Anyways this is a must to confirm before doing anything more.
I would check that before disassemble the throttle body.

Zanaqqq · Jul 21, 2026

DSMPT said:
Have you ever set the fixed SAS position properly before? The fixed SAS is with the IPS on 1g throttle body.
In case if the idle engine speed doesn't go down below a certain point by bottoming out the BISS, but if it does by loosing the fixed SAS (IPS), then most likely you would need to readjust the position of the fixed SAS and BISS. Anyways this is a must to confirm before doing anything more.
I would check that before disassemble the throttle body.

Where is the SAS? I don’t think I’ve ever heard of that before. My biss is bottomed right now.

pauleyman · Jul 21, 2026

Where is that red wire going? Youre missing a bolt on the throttle cable bracket.

Zanaqqq · Jul 21, 2026

pauleyman said:
Where is that red wire going? Youre missing a bolt on the throttle cable bracket.

I saw on another forum awhile that adding a ground to the throttle body there may help. It’s just another ground wire but I only had red wire at the time. And which bolt?

pauleyman · Jul 21, 2026

I also dont remember what vac lines go where but you have two open. Should probably look at that.

pauleyman · Jul 21, 2026

Zanaqqq said:
I saw on another forum awhile that adding a ground to the throttle body there may help. It’s just another ground wire but I only had red wire at the time. And which bolt?

That ground doesn't matter as you're 2g. 2g doesn't use the idle position switch. ECU shows throttle closed by TPS.

Zanaqqq · Jul 21, 2026

pauleyman said:
I also dont remember what vac lines go where but you have two open. Should probably look at that.

I had caps on them before I’ll put back on. I don’t really know where each one is supposed to go

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ECMlink 98 GST Idle tuning

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