1G throttle body BISS screw on 2G Talon

[carvinbassplyr]

I just want to clarify and make sure I understand what I've read as nothing I found was written super clear IMO regarding this. I have done the 1G throttle body swap on my 2G Talon TSi AWD and have some idle issues. Mainly, when I have to let off the throttle fast the car dies. This happens when driving and having to stop for a light and in neutral parked in the drive way. If I rev the engine up to 3500-4000 then slowly decelerate the car stays running, but if I rev the car up to the same RPM range and just let off the gas the car dies. I'm thinking this is a BISS screw problem although I have not yet set the TPS sensor. I know that for the 1G's you don't need a scan tool to set the BISS screw but this is a 1G throttle body on a 2G car so does the same apply? What should I do?

 

[RamenPride]

I have not yet set the TPS sensor.

you might want to do this first

 

[carvinbassplyr]

you might want to do this first

I hear ya, and I expected a few of these replies...I just have a sneaking suspicion that setting the TPS isn't going to cure the the stalling problem. Also, this throttle body didn't come with the SAS screw. Do I have to use/find the special OEM screw or can I just find a bolt with a matching thread pattern?

 

[carvinbassplyr]

No one knows about setting the BISS screw after a 1G throttle body swap?

 

[RamenPride]

I set the TPS and made sure the 1G throttle stop/closed throttle switch was adjusted properly. Let it warm up and turned the BISS in to bring the idle down. I think your supposed to hold the ISC in the middle setting using an appropriate scan tool and then adjust the BISS, but I haven't had any problems.

 

[carvinbassplyr]

Well, I set the TPS sensor per the instructions and the idle still doesn't settle below 1500 rpm's. So, looks like the BISS screw is the culprit. I'm debating whether to work with the BISS screw it came with or put in the new BISS screw I already have. I don't know that a shop around here will have the proper tool needed to properly set it so I really don't know what to do...

 

[snowborder714]

As long as the BISS o-ring doesn't seal, you can continue to use the one that's in there.

No, you don't need the tool. Get the car up to operating temp and slowly adjust it a little in one direction. Let it sit for a little to relearn the idle. Then repeat if necessary.

 

[steve]

Make sure you are using the 2G TPS and adjust it so you have a working IPS.

 

[TrevorS]

No one knows about setting the BISS screw after a 1G throttle body swap?

This BISS adjusts the stable floor, it doesn't adjust the dynamic behavior. Sounds like your problem is the dynamic behavior, and that implies sensors.

 

[steve]

The ISC handles the dynamic control but it has a limited range so the static adjustment of the idle speed is a requirement for the dynamic function. If the BISS is too far in or out, the ISC will be out of range and it won't be able to function.

The IPS tells the ECU when it should be using the ISC for dynamic control so it needs to be adjusted correctly and the ISC drivers on the ECU board need to be functional.

I don't know if any of the OBD2 scanners/dataloggers will tell you the ISC steps but if they do you want to set the BISS so that your getting about 12-30 steps at warm idle with any accessories off.

 

[carvinbassplyr]

Make sure you are using the 2G TPS and adjust it so you have a working IPS.

Yes, I used the 2G TPS off the original throttle body and adjusted it per the guidlines in the 1G throttle body swap write up. After the car has been running for about 15-20 min it settles down to 1500 rpm's and only drops to around 1400 rpm's if u push the clutch in. So I should mess with the BISS screw? Should I just put the new one in, or mess with the one already in there?

 

[V12 Killa]

Double check if the tb is closing and opening correctly. I had mines stay open slightly causing it to stall just like yours. But adjust the one in there to see if it fixes your idle.

 

[carvinbassplyr]

Double check if the tb is closing and opening correctly. I had mines stay open slightly causing it to stall just like yours. But adjust the one in there to see if it fixes your idle.

The TB closes fine. It stops when it hits the stop lever and opens smoothly. I haven't driven the car yet since setting the TPS properly so I don't know if that fixed the stalling problem at high speeds. Still have no solution for high idle.

 

[steve]

So I should mess with the BISS screw? Should I just put the new one in, or mess with the one already in there?

Unless there is something wrong with the one that's in there it shouldn't matter. The 1G and 2G BISS screws are/were identical but now your going to find either the original metal ones or the new plastic ones. I prefer the metal ones for no good reason.

If your idling at 1400, see if you can lower it by turning the BISS in but it it bottoms out and still idling too fast you'll have to figure out where the extra air is coming from.

 

[carvinbassplyr]

Still having a problem with this. There is, however, a new symptom. The rpms have started to shoot up between shifts as if I was keeping the pedal planted to the floor while shifting. This really concerns me as I don't want the motor to be red-lining between shifts and blow up. I still can't determine whether this a vacuum issue or something not set right.

 

[TJCTalon]

Check your ISC with an ohm meter. Should be between 28 and 32 ohms. Do you have dsmlink?

I know it was mentioned already but check our throttle cable.

 

[carvinbassplyr]

Check your ISC with an ohm meter. Should be between 28 and 32 ohms. Do you have dsmlink?

I know it was mentioned already but check our throttle cable.

Ok, I'll check that. Throttle closes all the way and unfortunately I do not yet have dsmlink

Well, I may finally be on to something. The 1g throttle body did not come with what I have now learned is a "throttle stop switch". Nothing in the the swap write up said anything about this sensor so I assumed I could just get any old screw and put it in there per the "1 and 1/4 turn from the point the screw touches" rule, but apperently there's a plug for this screw/ sensor that tells the car when you're off the throttle. Where does this plug into a 2g car? Where do I get one?

 

[steve]

That sensor on a 1G is the IPS which you should have inside the 2G TPS I talked about in post 8.

You want to adjust the stop so that it only keeps the butterfly from closing too far and sticking. It should otherwise fully close so that the only air flowing is via the BISS, ISC, and FIAV passages at idle.

On a 1G, the IPS is meant to be left alone but if it's been touched the adjustment is 15/16th of a turn after it touches and part of that is to push the pin in to activate the switch. If you using a bolt to replace the IPS it shouldn't even be that much since it will hold the butterfly open.

That would explain the high idle.

 

[carvinbassplyr]

That sensor on a 1G is the IPS which you should have inside the 2G TPS I talked about in post 8.

You want to adjust the stop so that it only keeps the butterfly from closing too far and sticking. It should otherwise fully close so that the only air flowing is via the BISS, ISC, and FIAV passages at idle.

On a 1G, the IPS is meant to be left alone but if it's been touched the adjustment is 15/16th of a turn after it touches and part of that is to push the pin in to activate the switch. If you using a bolt to replace the IPS it shouldn't even be that much since it will hold the butterfly open.

That would explain the high idle.

Ok, so from what I understand...the 4th wire on the 2g TPS is/takes the place of the IPS from the 1g setup. That being said, I shouldn't even turn the throttle stop screw a full turn after it touches the plate because it is only meant to stop the throttle plate from sticking and not as an idle adjustment screw like on most other cars. That still doesn't solve why the car dies if you let off the gas to quickly at higher speeds, but maybe it will help/remedy the high idle problem. Also it was suggested that ISC could be suspect. I saved the original throttle body and it has the ISC still in it as the 1g throttle body came with one already in it. I can just take the one off the original throttle body and put it on correct?

 

[steve]

They are interchangeable but you need to check the coils in both since a shorted coil will damage the ECU and an open coil won't step.

While the 2G manual tells you to turn the fixed SAS screw 1 1/4 turn, without knowing the thread pitch it's hard to compare that with the 1G IPS adjustment.

The factory cautions in both the 1G and 2G manuals not to touch the factory adjustment of either and it's clear why, this is the one of the most critical adjustment of the TB if you want the car to idle correctly.

 

[carvinbassplyr]

While the 2G manual tells you to turn the fixed SAS screw 1 1/4 turn, without knowing the thread pitch it's hard to compare that with the 1G IPS adjustment.

The factory cautions in both the 1G and 2G manuals not to touch the factory adjustment of either and it's clear why, this is the one of the most critical adjustment of the TB if you want the car to idle correctly.

Unfortunately the 1g throttle body I put on the car didn't come with that screw in place so I have to make do and try to find the correct setting. But what you're saying is that the proper setting for the 1g is only 15/16 of a turn because the thread pitch is larger than the 2g screw. I will try that.

 

[steve]

That's part of what I said.
The other part is that the IPS compresses first before the throttle butterfly starts opening and that included in the 15/16th so with just a regular bolt it shouldn't be turned that far or else it will hold the butterfly open farther than it should be.

 

[carvinbassplyr]

That's part of what I said.
The other part is that the IPS compresses first before the throttle butterfly starts opening and that included in the 15/16th so with just a regular bolt it shouldn't be turned that far or else it will hold the butterfly open farther than it should be.

So should I just slowly turn the screw in till it just stops the throttle plate from sticking?

 

[steve]

So should I just slowly turn the screw in till it just stops the throttle plate from sticking?

That's what I'm thinking. Not owning a 2G, I've never done this swap but that's how I would go about it.

I wish I had a spec for exactly how much, if any, clearance there should be between the butterfly and throttle bore when it's considered closed. That would eliminate the guesswork but it's not published.

 

[snowborder714]

This is how I do it for my 1g throttle body.
http://www.dsmtuners.com/forums/151826306-post2.html