Choosing the Right Spark Plugs for Your 1987-1991 Jeep Wrangler YJ
Keep your Wrangler's simple and rugged engine firing on all cylinders with the correct set of new spark plugs.
- For stock 1987-1991 Wrangler engines, inexpensive copper-core spark plugs from brands like Champion, Autolite, or NGK are the best choice.
- Always verify and set the spark plug gap to 0.035 inches before installation, regardless of the brand you buy.
- Expensive iridium or platinum plugs are not necessary and may not provide any benefit for the YJ's ignition system.
- Consider replacing the spark plug wires, distributor cap, and rotor at the same time for a complete ignition tune-up.
Symptoms of Failing Spark Plugs
Worn-out or fouled spark plugs can make your rugged YJ feel a lot less reliable. Because they are a primary wear item in the ignition system, they will eventually need to be replaced. Watch out for these common signs that your plugs are due for a change.
Choosing the Right Aftermarket Spark Plug
The ignition systems in the 1987-1991 Jeep Wrangler are straightforward and durable. They were designed in an era before complex engine management systems. Because of this, they generally perform best with simple, traditional spark plugs. Spending extra on high-tech plugs may not provide any noticeable benefit.
Plug Material: Copper is King
For these specific Jeep engines (2.5L I4 and 4.2L I6), standard copper-core spark plugs are the overwhelming recommendation from experienced owners and mechanics. They conduct electricity very well and are inexpensive. While plugs made from platinum or iridium last longer, they don't offer a significant performance advantage in this application and are not worth the extra cost. In some cases, they can even cause a weaker spark in the YJ's stock ignition system.
Brand Recommendations
- OEM & Value Tier (Recommended): Champion, Autolite, and NGK are the most frequently recommended brands. Champion was often the original equipment manufacturer (OEM) for these Jeeps, making them a safe and reliable choice. Many owners report excellent results with standard Autolite and NGK V-Power plugs, which are affordable and perform well in the 2.5L and 4.2L engines.
- Premium Tier: Brands like Denso and Bosch offer high-quality plugs. While their iridium options are available, their standard copper plugs are a better fit for the YJ.
- Jeep-Specific Brands: Crown Automotive and Omix-Ada are well-known for providing a wide range of Jeep replacement parts. For a universal part like a spark plug, they often re-brand a product from one of the major manufacturers. They can be a good option if you are ordering other Jeep-specific parts at the same time.
- Performance Tier: Accel offers plugs geared towards performance applications. Unless your engine is significantly modified, these are likely not necessary.
Pro Tip: Check The Gap!
No matter which brand you choose, you MUST check and adjust the spark plug gap before installation. The correct gap for most 1987-1991 Wrangler engines is 0.035 inches. An incorrect gap is a common cause of rough running and misfires, 🎬 Watch how to adjust your timing and carburetor for smoother idling. even with brand new plugs.
How Much Do New Spark Plugs Cost for a 1987-1991 Jeep Wrangler?
Spark plugs are an inexpensive maintenance item. The cost will depend on the brand and material you choose. A full set for your Wrangler should be very affordable.
| Category | Price Range (Per Plug) | Price Range (Set of 4 or 6) |
|---|---|---|
| New Aftermarket (Copper) | $3.50 - $6.00 | $14 - $36 |
| New Aftermarket (Iridium) | $15.00 - $36.74 | $60 - $220+ |
| Shop Labor | $80 - $150 | |
Note: Labor costs are estimates and can vary by location. The cost for a professional to replace the plugs is often higher than the parts themselves due to minimum labor charges. However, this is a very feasible DIY job.
🎬 Watch this step-by-step walkthrough for changing your YJ spark plugs.Frequently Asked Questions
How often should I change the spark plugs on my YJ Wrangler?
For these older Jeep engines using standard copper spark plugs, a good interval is every 30,000 miles or every two to three years. This ensures a strong spark and helps you monitor the engine's health by inspecting the old plugs.
What is a spark plug gap and why is it important?
The spark plug gap is the small, precise distance between the center electrode and the ground electrode. The ignition coil's voltage must jump this gap to create a spark. If the gap is too small, the spark can be weak; if it's too large, the spark may not happen at all. Setting the gap to the recommended 0.035 inches ensures the strongest, most consistent spark for your engine.
Should I replace my spark plug wires at the same time?
Yes, it's a great idea. Spark plug wires, along with the distributor cap and rotor, wear out over time. Replacing them all at once as part of a tune-up ensures the entire ignition system is in top shape and can prevent you from chasing down a misfire issue later.
🎬 See how to perform a full ignition tune-up on your Jeep.Are there any recalls for spark plugs on the 1987-1991 Wrangler?
No. There are no specific recalls or technical service bulletins (TSBs) from the NHTSA related to spark plugs for this vehicle generation. Any issues you encounter are typically due to normal wear and tear.
My 1991 Wrangler has the 4.0L engine. Does this advice still apply?
Yes, for the most part. The 4.0L inline-six engine was introduced in 1991. Like the 4.2L and 2.5L, it also runs best on standard copper-core spark plugs like Champion or NGK with a 0.035-inch gap. The fundamental advice to stick with simple, correctly gapped plugs remains the same.
Helpful Videos
Technical Specifications
OEM Part Numbers: 56027275 RFN14LY RC12LYC
Recommended Spark Plug Gap: 0.035 inches (for 2.5L I4 & 4.2L I6). Thread Size: M14x1.25. Hex Size: 5/8" (16mm).
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The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
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