Choosing the Right Spark Plugs for Your 1976-1988 Lotus Esprit
Keep your Esprit's high-performance engine firing on all cylinders with the correct set of plugs.
- The engine type (naturally aspirated vs. turbo) is the most critical factor in choosing the correct spark plug heat range.
- NGK is the most widely recommended brand by Esprit owners, with BPR6ES for NA engines and BPR7ES for turbos being common choices.
- Always check and adjust the spark plug gap to the factory specification (around 0.9mm) before installation.
- Water intrusion into the spark plug wells is a known issue that can cause misfires; keep the area clean and dry.
Symptoms of Failing Spark Plugs
Worn or incorrect spark plugs can cause noticeable problems in your Esprit. The most common signs include a rough idle, engine hesitation or stumbling during acceleration, and a general loss of power. You might also notice your engine is harder to start, fuel economy gets worse, or the engine misfires, which can feel like a stutter or jerk, especially under load. Ignoring these symptoms can lead to more significant engine issues over time.
A Note on Engine Differences
The 1976-1988 Lotus Esprit used different engines, primarily the naturally aspirated (NA) Type 907 and 912, and the turbocharged Type 910. Turbocharged engines run hotter and under higher pressures, so they require a 'colder' spark plug to prevent damage. Always verify which engine your Esprit has before purchasing plugs.
Choosing an Aftermarket Spark Plug
For a part like a spark plug, a high-quality aftermarket brand is often as good as or better than the original factory part. The most important factor is selecting the correct plug with the right specifications for your specific engine, not just the brand name. Owner forums and service data overwhelmingly point to one brand as the preferred choice.
Brand Recommendations
- Top Tier (Recommended): NGK is the most frequently recommended and used brand by Esprit owners and specialists. For naturally aspirated (NA) S1, S2, and S3 models, the NGK BPR6ES is a common choice. For turbocharged models, a colder plug like the NGK BPR7ES is often required to handle the extra heat.
- Good Quality Alternatives: Bosch and Champion are also excellent choices. Both were common original equipment suppliers for European cars of this era and produce plugs that meet the required specifications for the Esprit engines.
- Other Options: Autolite is a widely available brand that offers compatible plugs. MSD specializes in high-performance ignition systems and their plugs may be suitable for modified engines, but could be unnecessary for a stock setup.
Resistor vs. Non-Resistor Plugs
You will see plugs listed with codes like BP7ES and BPR7ES. The 'R' stands for resistor. Resistor plugs are designed to suppress radio frequency interference (RFI) that can cause static in your radio. Using a non-resistor plug in a car that needs one may cause interference with electronic components. Most Esprit models from this era specify a resistor plug (like BPR6ES or BPR7ES) to ensure stable ignition performance.
Cost for New Aftermarket Spark Plugs (1976-1988 Lotus Esprit)
| Category | Price Range (Set of 4) |
|---|---|
| Economy (e.g., Autolite) | $14 - $30 |
| Standard OE-Style (e.g., NGK, Bosch) | $18 - $45 |
| Premium (e.g., NGK Iridium) | $40 - $60 |
Frequently Asked Questions
How often should I change the spark plugs on my Esprit?
For standard copper or nickel spark plugs, a good interval is every 15,000 to 20,000 miles, or every two years. Given the age of the vehicle and the nature of its high-performance engine, regular inspection and replacement is cheap insurance against ignition problems. Some sources recommend replacement as often as every 28,000 miles for optimal performance.
What is the correct spark plug gap?
The recommended spark plug gap is typically 0.9mm. However, you should always verify the specification for your exact year and engine type. It is critical to check the gap on new plugs with a feeler gauge before installation and adjust if necessary. Do not assume they are pre-gapped correctly for your specific car.
Are there any known issues for Esprit spark plugs?
Yes, on some Esprit models, water can collect in the spark plug wells after washing the car or driving in heavy rain. This can cause the engine to misfire. It is a known issue, and if you experience a misfire after the engine bay gets wet, you should inspect the plug wells for water and dry them out. Using compressed air to blow out the wells before removing the plugs is a good practice.
Do I need special tools for the job?
Access to the spark plugs on an Esprit can be tight. A good quality spark plug socket (typically 5/8" or 16mm), a set of ratchet extensions, and a universal joint are highly recommended. A torque wrench is essential to tighten the new plugs to the correct specification to avoid damaging the engine's cylinder head.
Technical Specifications
Thread Size: 14mm. Thread Reach: 19mm. Socket Size: 5/8" (16mm) or 20.6mm depending on plug brand. Gap: ~0.9mm. Engine Type: Lotus 907, 910, 912.
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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.