Where is the PCV valve in a 1991 4.0 jeep wrangler and how do you replace it?

The PCV valve on a 1991 Jeep Wrangler 4.0L is located on the passenger side valve cover. It's a small, usually black or dark-colored, cylindrical valve that's usually easily visible once you lift the hood. It's often connected to a hose going to the intake manifold.

Here's how to replace it:

Tools you'll need:

* Socket wrench (likely a 5/16" or 7/16" depending on the size of the PCV valve retaining nut, double check beforehand)

* Socket extension (may be needed for better access)

* Rags or shop towels

* New PCV valve (ensure you get the correct replacement part for your 1991 Jeep Wrangler 4.0L)

Procedure:

1. Locate the valve: With the hood open, find the passenger side valve cover. The PCV valve is usually quite prominent; it's a small cylindrical valve, often sticking out somewhat from the valve cover.

2. Disconnect the hose(s): Carefully disconnect any hose(s) attached to the PCV valve. These may be a little stiff, so a gentle wiggle and some light pulling should suffice. Have rags ready to catch any oil that might spill.

3. Remove the PCV valve: Use the appropriate socket wrench to unscrew the PCV valve from its mounting location on the valve cover. It might be slightly snug, so apply moderate pressure.

4. Install the new PCV valve: Carefully screw the new PCV valve into the valve cover, tightening it just enough to secure it without over-tightening (over-tightening can damage the valve or its threads).

5. Reconnect the hose(s): Carefully reconnect the hose(s) to the new PCV valve.

6. Double-check: Make sure all connections are secure and there are no leaks.

7. Start the engine: After replacing the PCV valve, start the engine and listen for any unusual sounds or leaks. Check for vacuum leaks around the PCV valve area.

Important Notes:

* Engine off and cool: Always work on a cool engine. A hot engine can cause burns.

* Check your vehicle: While this is the typical location, it's always best to double-check a repair manual or online diagram specific to your 1991 Jeep Wrangler 4.0L to be absolutely sure of the PCV valve's location. Minor variations in placement can occur across years and models.

* Part Number: Obtain the correct PCV valve for your 1991 Jeep Wrangler 4.0L. Using the wrong part can cause problems. Your local auto parts store can assist you with finding the correct part using your vehicle's year, make, and model.

If you're uncomfortable performing this repair yourself, it's always best to take your Jeep to a qualified mechanic. This is a relatively simple job, but improper installation could lead to further engine problems.