1G High RPM with after market throttle body

[Austn17]

91 GST. i had bought a after market throttle body. no place for the idle stop switch. after install. cold start idles fine. idle is fine as long as i dont touch the throttle. once i start driving it it'll stay about 4k rpm on stops and shift through gears. do i need to some way mount the idle stop switch, stand alone ecu?

 

[DSMPT]

First, you should check the throttle cable moves smoothly and the throttle plate open/close smoothly. Sounds like the throttle plate is not fully returning once you open the throttle.

 

[jed344]

I agree, maybe your cable is to tight? set tension with the motor warm. Not uncommon for it to idle high if set when cold.

 

[Twinturbo120]

https://www.dsmtuners.com/threads/how-to-add-a-dsm-iac-to-any-aftermarket-throttle-body.448261/

 

[Vegas Smith]

91 GST. i had bought a after market throttle body. no place for the idle stop switch. after install. cold start idles fine. idle is fine as long as i dont touch the throttle. once i start driving it it'll stay about 4k rpm on stops and shift through gears. do i need to some way mount the idle stop switch, stand alone ecu?

There's a lot that could be wrong here. No stop switch is a bad thing and needs to be replaced unless that aftermarket tb is magically adjusted to the correct location. It's also bad because the ecu will not know when he car is at idle or when throttle is pressed down and will cause fueling issue. If you have ecmlink you can get around this lack of stop switch. Throttle cable is probably messed-up/incorrectly adjusted if you're' saying it's idling at 4k. We haven't even gotten to fiav and isc issues.

 

[ATF 2GTalon]

Also good to check if your FIAV gasket is not leaking. You're getting too much air in from somwwhere.

 

[jed344]

Think of it this way, if your cable is NOT to tight. Then air is leaking somewhere from TB or intake manifold. I actually had a high idle today around 1,500 rpm. After playing with idle tuning I had to reset biss adjust to get ISC to around 30 at idle. There is a lot that can cause it. Start with the easy stuff.