How do you adjust the idle speed of a 1993 jeep wrangler is set to high?

Adjusting the idle speed on a 1993 Jeep Wrangler's 4.0L engine (the most common engine in that year) isn't a simple turn-of-a-screw affair like on older carbureted vehicles. It's controlled electronically by the computer (PCM - Powertrain Control Module). A high idle could be caused by several things, and simply adjusting a screw (if you even find one) will likely mask a more serious underlying problem and potentially damage your engine.

Before attempting ANY adjustments:

* Check for vacuum leaks: A significant vacuum leak can cause a high idle. Inspect all vacuum hoses for cracks, loose connections, or damage. Pay close attention to the hoses leading to and from the throttle body, brake booster, and other vacuum-operated components.

* Check the throttle position sensor (TPS): A faulty TPS can send incorrect signals to the PCM, leading to a high idle. This often requires a multimeter to test its resistance and voltage output. A bad TPS is a common culprit.

* Check the IAC (Idle Air Control) valve: This valve regulates air flow at idle. A dirty or malfunctioning IAC can cause high idle. Cleaning it with throttle body cleaner (following the cleaner's instructions carefully) might solve the issue. However, if cleaning doesn't work, replacement may be necessary.

* Check the coolant temperature sensor: An inaccurate coolant temperature sensor can cause the PCM to adjust the idle incorrectly.

* Scan for diagnostic trouble codes (DTCs): Use an OBD-I code reader (specific to 1993 vehicles; OBD-II scanners won't work) to check for any trouble codes stored in the PCM. These codes will point to the most likely cause of the problem.

Where NOT to adjust (unless you know exactly what you're doing):

There might be an idle adjustment screw on the throttle body, but do not touch it without fully diagnosing the problem. Improper adjustment could cause drivability issues, poor fuel economy, and even damage your engine. The PCM controls the idle, and messing with this screw will likely disrupt the system's ability to self-regulate.

In short: Don't try to directly adjust the idle speed. Instead, systematically investigate the potential causes listed above. Using a diagnostic tool (OBD-I code reader) is crucial for proper troubleshooting. If you're not comfortable working on your Jeep's electrical and engine systems, it's best to take it to a qualified mechanic. Attempting to fix it yourself without proper knowledge could worsen the situation and lead to costly repairs.