You should NOT attempt to manually adjust anything on the throttle body. Doing so can damage the system and lead to serious drivability problems.
Here's what you should do instead:
1. Diagnose the problem: Before attempting any adjustments, determine *why* your idle is off. Is it too high, too low, rough, or surging? A problem with a sensor (like the IAC – Idle Air Control valve, TPS – Throttle Position Sensor, MAP – Manifold Absolute Pressure sensor, or coolant temperature sensor) can cause incorrect idle speed. A vacuum leak is another possibility. A simple diagnostic scan using an OBD-II scanner is recommended. Auto parts stores often offer this service for free.
2. Check for trouble codes: Use an OBD-II scanner to retrieve any diagnostic trouble codes (DTCs) stored in the PCM. These codes will point you towards the faulty sensor or system.
3. Inspect the IAC valve: The IAC valve is a critical component for idle control. Visually inspect it for cleanliness and proper operation. A dirty IAC can cause erratic idle. Cleaning it might resolve the issue, but replacing it might be necessary if cleaning doesn't help.
4. Check for vacuum leaks: A vacuum leak can cause low idle or erratic idling. Inspect all vacuum lines for cracks, holes, or loose connections. Pay close attention to lines connected to the brake booster, intake manifold, and PCV valve.
5. Professional help: Unless you're experienced in automotive diagnostics and repair, taking your S10 to a qualified mechanic is strongly recommended. Attempting to adjust the idle without understanding the electronic control system could lead to more serious and costly repairs.
In short: There's no simple "idle adjustment screw" on a 1994 Chevy S10. Fixing an idle problem involves diagnostics and potentially replacing faulty sensors or repairing vacuum leaks. A proper diagnosis is crucial before attempting any repairs.
