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2G FIAV block off, fixed high idle, now causing another idle issue

Misterflipster

Proven Member
87
21
Apr 5, 2020
sioux falls, South_Dakota
So yesterday i got the fiav blocked and now from a cold start i hold the throttle open and the car will eventually hold itself at 1k. However once i go to drive it and i put it under load, when i come off the gas it will die.

Other issue i have is that the car wont start after it warms up, im thinking its an alternator issue because it will run for some time and die on its own also. Dash lights flicker, i havent seen headlights flickering but yeah. I think its an alternator? My tuner suggested checking grounds (he believes the car might be relying on the chasis too much for ground??)
 

Misterflipster

Proven Member
87
21
Apr 5, 2020
sioux falls, South_Dakota
What's the history of the problem and the mod list for the car?
Alright this car is new to me, only owned it since august. But the mods that came on the car include:
-Tre stage 3 transmission
-Excedy stage I clutch
-Holset hx35
-Tial watsegate
-650cc injectors
-Dual springs
-272 delta cams
-.40 over wiseco pistons/eagle rods (6
bolt)
-Mbc boost controller
-Walbro 255 fuel pump
-Full exhaust carbon fiber tip
-Front mount intercooler
-Maf translator
-Gm 2.5 mas air flow sensor
' DSMlink ecu
-Forced performance turbo manifold
-Jmf intake manifold
-Aluminum radiator
-Turbo xs rfi blow off valve
It also has an EGR delete and i have relocated the battery to the trunk (both issues already existed prior to relocation)
It is a wiring nightmare but not sure if its a wire issue or not....i want to lean toward alternator because it doesnt seem to charge the battery while running? Its not pretty, im still trying to fugure out how i want to run all these god forsaken wires...
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Vegas Smith

20+ Year Contributor
5,035
2,908
Dec 2, 2002
Houston, Texas
You weren't lying. That is a mess. Capture a stream of the car running for 30 seconds with the car dying and upload it here as a picture so we can take a look.

and BTW, there is no GM MAF in that picture. Your car has no ability to measure airflow...........................
 

AWD-Tony

Supporting Member
6,803
3,690
Sep 11, 2017
Cincinnati, Ohio
There are two block offs available. One blocks off both iac and fiav, no holes. And the other blocks off just the fiav, two holes.

Complete block off will not allow the isc to have control over idle speed.

 

Misterflipster

Proven Member
87
21
Apr 5, 2020
sioux falls, South_Dakota
You weren't lying. That is a mess. Capture a stream of the car running for 30 seconds with the car dying and upload it here as a picture so we can take a look.

and BTW, there is no GM MAF in that picture. Your car has no ability to measure airflow...........................
Sorry, the tuner installed this in place of the MAF. I will try to get it running again, battery needs. Charging LOL

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You weren't lying. That is a mess. Capture a stream of the car running for 30 seconds with the car dying and upload it here as a picture so we can take a look.

and BTW, there is no GM MAF in that picture. Your car has no ability to measure airflow...........................

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

There are two block offs available. One blocks off both iac and fiav, no holes. And the other blocks off just the fiav, two holes.

Complete block off will not allow the isc to have control over idle speed.

Good information thank you. Im not sure if the IAC is deleted, just the EGR from my knowledge. Waiting for previous owner to respond.
 

AWD-Tony

Supporting Member
6,803
3,690
Sep 11, 2017
Cincinnati, Ohio
You said you installed the fiav block off, correct? Did the block off have holes?

When you block off fiav (fast idle air valve) you eliminated the function of fiav. With no fiav, you’ll have to hold the throttle open slightly durning cold starts.
 

Misterflipster

Proven Member
87
21
Apr 5, 2020
sioux falls, South_Dakota
Capture a log through ecmlink, not a video.
I barely installed ecmlink. Ive got zero clue how to use it honestly..the tuner was trying to work with it and yeah he replaced the MAF stuff with that other sensor.

You said you installed the fiav block off, correct? Did the block off have holes?

When you block off fiav (fast idle air valve) you eliminated the function of fiav. With no fiav, you’ll have to hold the throttle open slightly durning cold starts.
Correct, im aware as far as holding it for cold starts. But after it warms up, its idling on its own...THEN i put it in gear and give some gas, it moves....i take it out of gear and then it dies again.

That looks like a manifold pressure sensor designed for a 2G manifold. It has been modified.
Also as far as it being a "modified pressure sensor" does that mean its not going to work?
 

Justin DuBois

Proven Member
962
758
Aug 15, 2019
Oakland, California
Also as far as it being a "modified pressure sensor" does that mean its not going to work?
Depends on how it was modified.

I suspect the tuner is trying to configure ECMLink for Speed density?

Speed density does not use airflow for engine management - and generally people replace the airflow sensor (MAF) with a manfold pressure sensor (MAP) and Intake Air Temperature sensor (IAT)

You can use other pressure sensors that don't need to be modified if they are going to be plumbed with a hose.
 

Misterflipster

Proven Member
87
21
Apr 5, 2020
sioux falls, South_Dakota
Have you tried backing out the BISS (base idle speed setscrew)

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I backed it out a tiny bit, but from another thread they were saying once you delete the FIAV you HAVE to screw the BISS all the way in?? Is that correct?
 

Misterflipster

Proven Member
87
21
Apr 5, 2020
sioux falls, South_Dakota
Uuuh, well the BISS simply lets more or less air past the closed throttle plate. Idle too high - close it down, idle too low, open it up.
Right, i normally have the BISS two full turns from closed, as i also read in a post....but yeah these guys were saying that after the block off plate is installed, it needs to be turned in all the way
 

Justin DuBois

Proven Member
962
758
Aug 15, 2019
Oakland, California
Right, i normally have the BISS two full turns from closed, as i also read in a post....but yeah these guys were saying that after the block off plate is installed, it needs to be turned in all the way
Two full turns from closed is a stock starting point. Right now, you just need the thing to keep running. Try it and see if there is any affect to your idle.

The best setting for the BISS is based on a warmed up engine, looking in ECMlnink at the ISC stepper motor position. You want it to hover somwhere around 30. This is assuming the ISC is doing its job, and not electronically defective or all gummed up with junk.
 

Misterflipster

Proven Member
87
21
Apr 5, 2020
sioux falls, South_Dakota
Two full turns from closed is a stock starting point. Right now, you just need the thing to keep running. Try it and see if there is any affect to your idle.

The best setting for the BISS is based on a warmed up engine, looking in ECMlnink at the ISC stepper motor position. You want it to hover somwhere around 30. This is assuming the ISC is doing its job, and not electronically defective or all gummed up with junk.
Wow...LOL that actually worked, ish...cant completely confirm yet, dropping battery off to charge at oreillys

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Last edited by a moderator:

dwb

Proven Member
312
157
Sep 9, 2021
Broomfield, Colorado
I backed it out a tiny bit, but from another thread they were saying once you delete the FIAV you HAVE to screw the BISS all the way in?? Is that correct?
No, the FIAV is only for cold starts. Once the engine is up to temp, a properly working FIAV will close and it's no different than a FIAV-only block-off.

Make sure you check the Vfaq for setting your base idle. http://www.vfaq.com/mods/BISS-2G.html
 

Misterflipster

Proven Member
87
21
Apr 5, 2020
sioux falls, South_Dakota
Two full turns from closed is a stock starting point. Right now, you just need the thing to keep running. Try it and see if there is any affect to your idle.

The best setting for the BISS is based on a warmed up engine, looking in ECMlnink at the ISC stepper motor position. You want it to hover somwhere around 30. This is assuming the ISC is doing its job, and not electronically defective or all gummed up with junk.
Update: even with the BISS opened more it still wants to die...not always, sometimes it will hold idle, other times it will die, especially when the car is warm. Bur i am 95% sure my alternator is bad and could be contributing to the problem...car was at 12.15 initially....started it and the alternator actually DID charge it up to 12.18 then i drove it (car died cuz of idle) and when i checked it dropped down to 12.10 (only went around the block)
 

Justin DuBois

Proven Member
962
758
Aug 15, 2019
Oakland, California
Update: even with the BISS opened more it still wants to die...not always, sometimes it will hold idle, other times it will die, especially when the car is warm. Bur i am 95% sure my alternator is bad and could be contributing to the problem...car was at 12.15 initially....started it and the alternator actually DID charge it up to 12.18 then i drove it (car died cuz of idle) and when i checked it dropped down to 12.10 (only went around the block)
If it dies approaching a stop sign, or when you turn on the AC - this might indicate a problem with the ISC. (idle speed controller) There is an ohm meter test you can do on the ISC pins with the harness disconnected. This will tell you if the coils that drive the stepper are connected. Bad Coil = Bad Idle control. The air passage behind the ISC may also be gummy with carbon and oil preventing the ISC from moving. if you remove the ISC, make sure its nice and clean - using break-clean or carb cleaner etc. Look for these diagnostic and maintenance steps in the service manual for more detail.
 

Misterflipster

Proven Member
87
21
Apr 5, 2020
sioux falls, South_Dakota
If it dies approaching a stop sign, or when you turn on the AC - this might indicate a problem with the ISC. (idle speed controller) There is an ohm meter test you can do on the ISC pins with the harness disconnected. This will tell you if the coils that drive the stepper are connected. Bad Coil = Bad Idle control. The air passage behind the ISC may also be gummy with carbon and oil preventing the ISC from moving. if you remove the ISC, make sure its nice and clean - using break-clean or carb cleaner etc. Look for these diagnostic and maintenance steps in the service manual for more detail.
Thank you for the constitent help! Its made a big difference already! As far as the ISC where is it located(on the throttle body?) And i am doing this test on the senor itself then?

If it dies approaching a stop sign, or when you turn on the AC - this might indicate a problem with the ISC. (idle speed controller) There is an ohm meter test you can do on the ISC pins with the harness disconnected. This will tell you if the coils that drive the stepper are connected. Bad Coil = Bad Idle control. The air passage behind the ISC may also be gummy with carbon and oil preventing the ISC from moving. if you remove the ISC, make sure its nice and clean - using break-clean or carb cleaner etc. Look for these diagnostic and maintenance steps in the service manual for more detail.
Okay, so i found a youtube video that goes over this, and i got 40 across all pins
 

Justin DuBois

Proven Member
962
758
Aug 15, 2019
Oakland, California
Thank you for the constitent help! Its made a big difference already! As far as the ISC where is it located(on the throttle body?) And i am doing this test on the senor itself then?
Here is a site from the past with all kinds of good data from the folks who were figuring things out long time back:
Unfortunately - this link I wanted you to see is dead: http://dmtalon.v8eaters.com/ISC.html

So - back to the search for you. I'll get a couple pictures of a throttle body up here shortly so you can see where the ISC is located.

Lots of 1G throttle body pics here:
This is the ISC - removable 2 bollts
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Last edited:

Misterflipster

Proven Member
87
21
Apr 5, 2020
sioux falls, South_Dakota
Here is a site from the past with all kinds of good data from the folks who were figuring things out long time back:
Unfortunately - this link I wanted you to see is dead: http://dmtalon.v8eaters.com/ISC.html

So - back to the search for you. I'll get a couple pictures of a throttle body up here shortly so you can see where the ISC is located.
I will look into that link. I know where the ISC is after looking at a youtube video. When i OHMed the pins on the ISC it was 40 across all the pins

If it dies approaching a stop sign, or when you turn on the AC - this might indicate a problem with the ISC. (idle speed controller) There is an ohm meter test you can do on the ISC pins with the harness disconnected. This will tell you if the coils that drive the stepper are connected. Bad Coil = Bad Idle control. The air passage behind the ISC may also be gummy with carbon and oil preventing the ISC from moving. if you remove the ISC, make sure its nice and clean - using break-clean or carb cleaner etc. Look for these diagnostic and maintenance steps in the service manual for more detail.
Thank you for the pictures! Yup those are what i tested and got 40. So do i still need to take it off then to see if its gummed up? Or if im getting the readings it should be fine?
 
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