If your S-10 remains on high idle after starting, it could be due to a malfunctioning idle air control (IAC) valve, which regulates engine idle speed. A vacuum leak can also cause an elevated idle by allowing extra air into the intake manifold. Additionally, issues with the throttle position sensor (TPS) or a cold engine in cooler temperatures can lead to higher idle speeds. It’s advisable to have these components checked for proper function.
If this happened all at once, check the vacuum lines. A cracked or broken line will cause high or rough idle.
A high idle could be caused by a vacuum leak, a failed engine-to-chassis ground strap or a gooped-up IACV. You should also check the PVC valve.
The idle sensor on a 1991 S10 4.3 can be located at the engine bay.
throttle positioning sensor, egr, idle air control
You don't. The ECM (Engine Control Module) maintains the correct idle speed. If the idle is out of control you probably have a vacuum leak.
Idle Air Control Valve
Yep!
check for a vacuum leak.
The idle is controlled by the ecm, no adjustment needed. If you are having idle problems look for a vacuum leak or possibly a faulty idle air control valve (IAC).
No it does not.
security light on 1998 s10 start but cut off
You can't, It is not adjustable. The idle is controlled by the idle speed control solidnold that is screewed into the left side of the throttle body. It may need to be removed and cleaned.