Throttle closed position switch

[gcihlar]

So I have a issue with my idle where it surges from 800 to 1500 rpms up and down and doesn't stop. replaced all the gaskets in the throttle body cleaned the throttle body put it back together and problem is still there, unplugged the throttle close position switch and the idle is perfect just hight at like 2,000 rpms. Does this mean the switch is bad?

92 talon tsi

 

[Absit]

No, it probably means your BISS isn't adjusted properly. Searching is super awesome.

 

[gcihlar]

No, it probably means your BISS isn't adjusted properly. Searching is super awesome.

you are correct searching is fun thats why i did it first, adjusting the biss doesn't stop idle surge............

 

[Absit]

you are correct searching is fun thats why i did it first, adjusting the biss doesn't stop idle surge............

Are you saying adjusting the BISS doesn't help with idle surge, or you adjusted your BISS and it didn't help?

If the first, good luck.

If the second, how did you adjust it? If you did it right, you may have an FIAV leak. You did an actual boost leak test and didn't just start replacing gaskets, right?

 

[gcihlar]

Are you saying adjusting the BISS doesn't help with idle surge, or you adjusted your BISS and it didn't help?

If the first, good luck.

If the second, how did you adjust it? If you did it right, you may have an FIAV leak. You did an actual boost leak test and didn't just start replacing gaskets, right?

did a boost leak test and the seals on the throttle shaft were leaking replaced those in the process replaced the gaskets for the throttle body elbow and the throttle body to intake manifold, also fiav gasket, retested no leaks. when i unplug the tcps it idles fine just at 2,000 which by adjusting the biss screw I can get it to come down to normal, but once i plug the tcps back in then the idle starts jumping up and down right away.

I may be wrong, but doesn't the biss screw just adjust what rpm's it idles at buy screwing it in or out?

 

[Absit]

That's not how you adjust the BISS. Search for the proper method of BISS adjustment (I think there's a copy on VFAQ too) and you may find your problem fixed. When you disconnect the Idle Switch the car doesn't know it's idling, so the ISC stops doing anything. You can get the idle down and that's cool, but when you connect the Idle Switch again the car knows it's idling and the ISC tries to control things again. Adjust your BISS properly and if it still doesn't work your ISC may be bad, test it. If the ISC is good and the BISS doesn't help, you probably have an FIAV leak. Disable or block the FIAv or replace the throttle body.

 

[gcihlar]

That's not how you adjust the BISS. Search for the proper method of BISS adjustment (I think there's a copy on VFAQ too) and you may find your problem fixed. When you disconnect the Idle Switch the car doesn't know it's idling, so the ISC stops doing anything. You can get the idle down and that's cool, but when you connect the Idle Switch again the car knows it's idling and the ISC tries to control things again. Adjust your BISS properly and if it still doesn't work your ISC may be bad, test it. If the ISC is good and the BISS doesn't help, you probably have an FIAV leak. Disable or block the FIAv or replace the throttle body.

ok I found it and i will give this a try tom, my isc was tested good so i will try adjusting the biss thank you