I have an 86 Corvette and today I pulled off the throttle body. I wanted to clean the IAC sensor because the car had trouble starting when hot. I clean the IAC sensor and thottle body and replace it. Now the car shuts off immediatly after starting, unless I hold down the gas in which case it idles rough until I let off the gas and it shuts off. Any suggestions on what the problem might be?
My first thought is that the IAC (= idle air controller, it is not a sensor) pintle position may have changed during the process, and that it doesn’t move like it should. If that’s the case, it could be either a faulty IAC or a lack of signal to the IAC. The choice would be to have the system tested, or replace the IAC to see if that fixes it and if it doesn’t then have the system tested.
On my car it is very easy to attach the IAC backwards. Check on that. There should be an arrow to indicate the flow direction.
Also, make sure you reattached all of the vacuum hoses to the throttle body. A disconnected vacuum hose can cause the engine to behave as you’re describing.