A Guide to Spark Plugs for the 2007-2012 Mitsubishi Eclipse
Fix that rough idle and restore your Eclipse's performance by choosing the right spark plugs.
- Choose Iridium spark plugs from NGK or Denso for the best performance and longest life, as they are often OEM quality.
- The replacement job is simple for the 2.4L 4-cylinder (GS) engine but complex for the 3.8L V6 (GT) engine, which requires removing the intake plenum.
- While replacing plugs, inspect the spark plug wells for oil, which indicates a failing valve cover gasket that should also be replaced.
- No recalls or major TSBs have been issued for spark plugs on this Eclipse generation.
Is Your Eclipse Running Rough? It Could Be the Spark Plugs.
If your 2007-2012 Mitsubishi Eclipse is experiencing a rough idle, has trouble accelerating, or the check engine light has come on, it might be time for new spark plugs. These small parts play a huge role in your engine's health. Over time, the electrodes wear down, get covered in carbon, and can't produce the strong spark your engine needs. This guide will help you understand the symptoms of failure and choose the best aftermarket replacements for your specific Eclipse model.
Symptoms of Failing Spark Plugs
🎬 Watch: A visual guide to common symptoms of bad spark plugs.
- Rough Idle: The engine may shake or vibrate more than usual when you're stopped.
- Engine Misfires: You might feel a hesitation or stumble during acceleration. This can also trigger a flashing check engine light with codes like P0300, P0301, etc.
- Poor Acceleration: The car feels sluggish and doesn't respond as quickly when you press the gas pedal.
- Reduced Fuel Economy: You're visiting the gas station more often because worn plugs lead to inefficient fuel combustion.
- Trouble Starting: Weak plugs struggle to create the initial spark needed to fire up the engine.
Important: 4-Cylinder vs. V6 Engine Differences
The replacement job for spark plugs on a 4th generation Eclipse is very different depending on your engine. Before you buy parts or start the job, you must know if you have the GS (2.4L 4-cylinder) or GT (3.8L V6) model.
- 2.4L I4 (GS Models): This is a straightforward job. The spark plugs and ignition coils are located directly on top of the engine, under a plastic cover. Access is easy, making this a great DIY project for beginners. 🎬 See this quick walkthrough for replacing plugs on the 2.4L engine.
- 3.8L V6 (GT Models): This job is much more complex. While the front three spark plugs are easy to access, the rear three are hidden underneath the upper intake plenum (a large part of the engine's air intake system). This plenum must be removed to reach the rear plugs, adding significant time and difficulty. This is best left to experienced DIY mechanics or a professional shop. 🎬 Watch this detailed guide for the complex V6 spark plug replacement.
V6 Owners: Be Prepared
If you have the 3.8L V6 engine, be aware that replacing the rear spark plugs requires removing the upper intake plenum. This adds several hours to the job and requires careful disassembly and reassembly of gaskets, bolts, and hoses.
Choosing the Right Aftermarket Spark Plugs
Not all spark plugs are created equal. For the Eclipse, using a high-quality Iridium plug is recommended for longevity and performance, as they are often the original equipment type. Cheaper plugs will work, but you'll be replacing them much sooner.
| Brand Tier | Brands | Quality & Performance Assessment |
|---|---|---|
| Top Tier / OEM Equivalent | NGK, Denso | NGK and Denso are the original equipment suppliers for many Japanese vehicles, including Mitsubishi. Their Iridium plugs (like NGK Laser Iridium or Denso Iridium Long Life) offer the best performance, durability, and longest life, often lasting up to 100,000 miles. These are the recommended choice for a hassle-free, long-term solution. |
| Mid-Tier | Bosch, Champion | Bosch offers quality Iridium and Double Platinum plugs that are a solid alternative to OEM. Champion is a well-known brand that provides reliable performance. These are good options if you're looking for a balance between cost and quality. |
| Standard / Budget | Autolite, Skyward | These brands offer more affordable copper or platinum plugs. They will function correctly but will have a significantly shorter lifespan than Iridium plugs, requiring more frequent changes (typically every 30,000 miles). |
| Performance | MSD | MSD specializes in high-performance ignition systems. Their spark plugs are geared towards modified engines and are not necessary for a stock Eclipse. |
A Note on Gapping
Modern Iridium spark plugs from brands like NGK and Denso come pre-gapped from the factory. It is best not to adjust the gap unless you have the proper tool and confirm it is incorrect. Attempting to gap these plugs with the wrong tool can easily break the fine iridium tip.
Frequently Asked Questions (FAQ)
How often should I replace the spark plugs on my Eclipse?
For high-quality Iridium plugs (like NGK or Denso), a replacement interval of 60,000 to 100,000 miles is typical. If you use standard copper or platinum plugs, you should plan on changing them every 30,000 miles.
Are there any recalls for the spark plugs on the 2007-2012 Eclipse?
No. Searches of the National Highway Traffic Safety Administration (NHTSA) database show no recalls or technical service bulletins (TSBs) specifically related to spark plugs or the ignition system for this vehicle generation.
What else should I inspect when changing my spark plugs?
When you remove the ignition coil, inspect the spark plug tube for oil. Oil in this area indicates a leaking spark plug tube seal, which is part of the valve cover gasket. If oil is present, you should plan to replace the valve cover gasket set soon to prevent ignition coil failure.
Do I need special tools to change my spark plugs?
You will need a ratchet with extensions, a 10mm socket for the coil bolts, and a 5/8-inch spark plug socket. A torque wrench is highly recommended to tighten the new plugs to the correct specification (around 18 ft-lbs for the 2.4L engine) to avoid damaging the engine's cylinder head.
Helpful Videos
Technical Specifications
OEM Part Numbers: MN158596 (For 2.4L Engine) 1822A002 (For 3.8L Engine)
Spark Plug Socket Size: 5/8 inch. Spark Plug Gap (2.4L): Approx. 0.028-0.031 in (though most Iridium plugs are pre-gapped). Torque Spec (2.4L): Approx. 18 ft-lbs.
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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.
- Mitsubishi Eclipse:
- 🎬 Helpful Videos
- 🛍️ Shop This Part
- Is Your Eclipse Running Rough? It Could Be the Spark Plugs.
- Symptoms of Failing Spark Plugs
- Important: 4-Cylinder vs. V6 Engine Differences
- V6 Owners: Be Prepared
- Choosing the Right Aftermarket Spark Plugs
- A Note on Gapping
- Frequently Asked Questions (FAQ)
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