Resolved 1G Closed Throttle Switch causing Idle Surge

[BoostedTT91]

I just rebuild the engine and put a new non turbo throttle body on and the FIAV is completly blocked off. I dont have any vacuum leaks that i could find anywhere and with the closed throttle switch has the ground wire hooked up to it, the car idle surges like crazy and when i remove the ground it completly stops. What would be causing this now that i dont have a IAC or FIAV. Would leaving the wire disconnected hurt anything? What exactly is that doing when its hooked up?

 

[allthrottle]

I don't have much insight about what the ctps does or what it's function is, besides telling the ecu when the throttle is closed. I did have mine rigged up from the previous owner when I first bought my car, and it broke off. I didn't have a chance to fix it for a week, so drove around with it hanging/unplugged. I didn't notice any major difference while driving city or highway, though I did notice once or twice the CEL come on while holding a constant speed/throttle on the highway for a few minutes. It cleared up after getting on it a little.

 

[steve]

Idle Position Switches don't cause Idle Surge.

Idle Surge is when the car doesn't run below the threshold programmed into the ECU for the current coolant temp. When the IPS is disconnected the ECU thinks the throttle is open and so it doesn't check. That's why connecting it resulted in surging because the idle was too high all along.

The hunt should be for why the car isn't idling low enough since that's really the problem.

 

[Lofty]

The Idle Switch is basically saying, "Oh the throttle is closed now."
Then the ECU realizes that the idle is to high, so you get fuel cut.
When the idle drops below 1500 or so, the ecu thinks "Hey, I can give stop adjusting the fuel now" and it goes right back up.

Although leaving the wire unplugged will not cause many problems, you will have a higher after you have a load on the engine. But it's not too bad, mines unplugged right now because I hate the rolling fuel cut.

Too much air is getting past the tp, plain and simple.
Is the Throttle plate closing all the way?
Is the cable too tight?
The Idle switch can be adjusted, if you adjust it too far you push the TP a little bit open.
If your ISC has just been replaced, check it anyways.

Best of luck, you'll find it.

 

[BoostedTT91]

i had the throttle switch adjusted down to far in turn the TB was open to much. I backed it out some and the surge is gone