Choosing the Right Spark Plugs for Your 1987-1989 Chrysler Conquest
Keep your Conquest's 2.6L turbo engine running strong with the correct spark plugs.
- For best performance, use standard copper spark plugs like the NGK BPR6ES or Denso W20EPR-U.
- Avoid expensive platinum and iridium plugs, as they are not known to work well with the Conquest's engine.
- Always check and set the spark plug gap to between 0.031" and 0.035" before installation.
- Replacing spark plugs is an easy DIY task that can be done in under an hour with basic tools.
Symptoms of Failing Spark Plugs
Worn-out spark plugs can cause noticeable problems in your Conquest. Because they are so critical to the combustion process, even a small issue can affect how your car drives. Look out for these common signs:
🎬 Watch: See a visual guide to symptoms of bad spark plugs- Rough Idle: The engine may shake or vibrate more than usual when stopped.
- Engine Misfires: You might feel a hesitation or stumble during acceleration. The engine may sound uneven.
- Reduced Power: Your car may feel sluggish and slow to respond when you press the gas pedal.
- Poor Fuel Economy: If you're filling up your gas tank more often, failing plugs could be the cause. Inefficient combustion wastes fuel.
- Difficulty Starting: Weak or fouled plugs can make it hard for the engine to start, especially when cold.
Choosing the Right Aftermarket Spark Plug
The Chrysler Conquest uses a Mitsubishi-designed engine (the G54B), and owner experience shows it performs best with specific types of spark plugs. While modern platinum and iridium plugs offer long life in many cars, the consensus for the Conquest is that traditional copper plugs provide the best performance. They may need to be changed more often, but their performance in this engine is consistently rated highest by enthusiasts.
Spark Plug Brand Recommendations
| Tier | Brands & Models | Notes |
|---|---|---|
| Top Tier (Highly Recommended) | NGK (BPR6ES), Denso (W20EPR-U) | These are the go-to plugs for Conquest and Mitsubishi Starion owners. The NGK BPR6ES is the most frequently recommended plug for stock or lightly modified engines. The Denso W20EPR-U is a direct cross-reference and another excellent choice from a trusted Japanese brand. |
| Mid-Grade / Alternatives | Bosch (WR7D), Champion (RN9YC) | These are reliable brands that offer direct-fit copper plugs. While not as commonly praised as NGK or Denso in enthusiast forums for this specific car, they are a perfectly acceptable alternative if the top-tier plugs are unavailable. |
| Economy | Autolite (4263) | Autolite provides a budget-friendly option that meets the basic requirements for the engine. It's a functional choice for daily driving. |
| Not Recommended | Platinum & Iridium Plugs | Despite being more expensive, multi-tip, platinum, and iridium plugs are generally not recommended for the Conquest's G54B engine. Owners report they can cause running issues and do not offer a performance benefit over standard copper plugs in this application. |
Check the Gap! Even if plugs come "pre-gapped," you should always verify the gap before installation. 🎬 Watch: How to properly gap your new spark plugs For a stock 1987-1989 Conquest, a spark plug gap between 0.031" and 0.035" is the recommended starting point. An incorrect gap can cause misfires and poor performance.
Known Issues & Bulletins
No safety recalls have been issued by the NHTSA for spark plugs on the 1987-1989 Chrysler Conquest. However, Chrysler did issue a Technical Service Bulletin (TSB) in May 1989 titled "Spark Plug Usage - Service Manual Revision" (TSB #180189). While the exact text is not widely available, the title suggests that the manufacturer released updated information on the correct spark plugs to use after the cars were already in service, highlighting the importance of using the right part.
Frequently Asked Questions (FAQ)
How often should I replace the spark plugs on my Conquest?
When using the recommended conventional copper spark plugs (like NGK BPR6ES), a replacement interval of every 15,000 to 30,000 miles is a good practice to maintain peak performance.
What is the correct spark plug gap for a stock 1987-1989 Conquest?
The recommended gap is between 0.031 inches (0.8mm) and 0.035 inches (0.9mm). Always use a gap tool to check and adjust the new plugs before installing them.
Can I use iridium or platinum spark plugs for longer life?
You can, but it is not recommended by the enthusiast community for this specific engine. Owners consistently report the best and most reliable performance comes from standard copper plugs. Using more expensive plugs may not provide any benefit and could potentially cause running issues.
Is changing the spark plugs a difficult job?
No, this is a great DIY job for beginners. The spark plugs on the 2.6L engine are easily accessible. You will need a ratchet, a 13/16" (21mm) spark plug socket, and a gap tool.
🎬 Watch: Step-by-step DIY tutorial for changing your spark plugsHelpful Videos
Technical Specifications
OEM Part Numbers: MS851233 MS851232
Thread Size: 14mm, Hex Size: 13/16" (21mm), Seat Type: Gasket, Recommended Gap: 0.031" - 0.035" (0.8mm - 0.9mm).
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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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