ECMlink No leaks - 0 ISC steps - High Idle

[Justin DuBois]

I've been tryng to get my idle down to my 800rpm target, but it just barely sits there when everything is good an warmed up. The ISC shows 0 most of the time, but if I put some load on with the AC, then it jumps up and has better control.

I've boost leak tested, and there is nothing leaking.
The BISS is all the way closed, so there is no more room to adjust there
I'm still using a stock 1G FIAV plumbed with coolant lines, and it does the bulk of the work. On first start start, Idle is 2000k, then as the coolant temps warm up, it drops to 1000, and very very slowly drops to 900.

Any suggestions?

 

[Stapl3]

Throttle plate cracked too far open? Throttle stop should be 15/16th of a full turn clockwise from closed.

 

[USMCGSX]

I had this same symptom after rebuilding my TB shaft seals, but only when the car was up to temp. Was fine cold.
Never messed with the throttle stop screw changing out the shaft seals, so I assumed it was another ezpz rebuild and good to go.
Drove me nuts trying to figure it out, but after much tinkering and cursing, someone advised me to loosen those 2 screws holding the plate to the shaft, then turn the throttle open and clap it a few times before i tighten the screws on the shaft securing the plate. Worked like a charm.
Guess when it got warm, things expand, and the TB plate was catching on something and just barely not closing all the way and causing idle to be high.
May not be the source of your problem, but it's quick and easy and might just save your back and some aggravation.

 

[pauleyman]

I've been tryng to get my idle down to my 800rpm target, but it just barely sits there when everything is good an warmed up. The ISC shows 0 most of the time, but if I put some load on with the AC, then it jumps up and has better control.

I've boost leak tested, and there is nothing leaking.
The BISS is all the way closed, so there is no more room to adjust there
I'm still using a stock 1G FIAF plumbed with coolant lines, and it does the bulk of the work. On first start start, Idle is 2000k, then as the coolant temps warm up, it drops to 1000, and very very slowly drops to 900.

Any suggestions?

Make sure your throttle is actually closing. Push on it. If it's hanging find out why. Cable, seals catching etc. Cable is a common culprit especially if you've messed around in that area recently.

 

[Justin DuBois]

Make sure your theittlw is actually closing. Push on it. If it's hanging find out why. Cable, seals catching etc. Cable is a common culprit especially if you've messed around in that area recently.

Good reading here - I'm trying the full slack when closed approach with the cable.

Dsm Idle Control | Six Sigma Dyno Tuning | United States

DSM Idle control by Six Sigma Tuning

www.sixsigmatuning.com

Grabbing the throttle plate, and applying some more close pressure didn't seem to do anything, but I'm going to loosen the stop/closed position switch, and see if that make any difference.

 

[dwb]

Keep in mind the FIAV may be leaking even when up to temp. That's what gave me idle issues galore until I blocked it off.

 

[Justin DuBois]

-24
I got it in the ballpark, with no room for adjustment. Backing off the close stop did get the ISC involved in the idle control process. 0.63v-5.00v on the TPS sensor, BISS is (unfortunately) closed completely - but it did turn down to get the ISC from -13 to -24 - 180-212deg f on the coolant temps - fans cycling on and off.

 

[steve]

The TB is really sensitive to make the idle work right. I ruined my first TB just by cleaning off the black compound the factory used to seal the edges of the throttle butterfly. I thought it was carbon and scrubbed it all away. This is one of the reasons they warn about touching the IPS adjustment. It doesn't take much air going around the butterfly to make a bad day. You pretty much want it closed but not biting into the throttle bore.

Then there is the FIAV. Same deal, it pretty much needs to fully close and seal off it's bypass passage when the coolant is hot.

Also look closely at where the ports on the TB come out inside. Some are on the intake side of the butterfly and at least one is on the manifold side. If you loop them it becomes another bypass source.

Hopefully the brake booster check valve, BOV, FP solenoid, etc and the PCV value aren't leaking cause they are another potential bypass source and they don't always show up easily doing a BLT.

 

[Stapl3]

-24
I got it in the ballpark, with no room for adjustment. Backing off the close stop did get the ISC involved in the idle control process. 0.63v-5.00v on the TPS sensor, BISS is (unfortunately) closed completely - but it did turn down to get the ISC from -13 to -24 - 180-212deg f on the coolant temps - fans cycling on and off.

Negative numbers? The ISC has an operating value of 0-120. We aim to put it at 30 just because it's going to add air most likely than remove it. That gives it some room to remove and most of the room to add. And the 30 is achieved with the radio off, headlights off, doors closed, AC off, not moving the steering wheel, etc etc.

As I said throttle stop is 15/16 and afaik the BISS is two full turns out from fully in. If you apply those two constants, it really comes down to how else is the air entering the manifold.

I have only had bad luck messing with the FIAV and never recommend it.
You are simulating the throttle stop switch based on TPS position, right?

On first start start, Idle is 2000k, then as the coolant temps warm up, it drops to 1000, and very very slowly drops to 900.

This is completely normal operation. Are you targeting 800 in 'link? The target rpm there I feel is arbitrary. Some cars love to idle at 850, 900, 925, etc while hate to idle 50rpm either way. It's almost like the engine decides more-so than we do. It's like a rhythm and there's SO many variables. It's fun to play with and you just kinda feel out what seems correct.

 

[Justin DuBois]

Oops, I transposed it
On the logger it shows 24 -

I'm using a 2G TPS, with the 4th pin for the close switch.
The 1G Close-Switch - is not wired, but it is being used as the close stop.

Stock 2G idle RPM is 750+- 100rpm

This is a number I need to hit to pass CA Emissions tests

 

[99dsmer4g63]

On a 2g 4 wire tps as soon as you touch the sas you need to re adjust the tps’s internal ips.

Biss I usually go all in and then end up around 2-2.5 turns out.

It is important to adjust the tb in the correct steps or you will chase yourself in a circle.

-Daniel