Choosing the Right Spark Plugs for Your 1985-1991 GMC Safari
Keep your Safari's engine running smoothly with the correct new aftermarket spark plugs.
- ACDelco is the OEM-equivalent choice and is highly recommended, but brands like NGK and Denso are also excellent options.
- The job is known to be difficult due to poor access, especially for the rear plugs on the 4.3L V6. Removing the front wheels and inner fender liners can make it much easier.
- Always verify your engine size (2.5L I4 or 4.3L V6) before purchasing, as they use different plugs.
- For 1991 models, use a deep spark plug socket to avoid damaging the longer ceramic insulator on newer plug designs.
Signs of Failing Spark Plugs
Worn-out spark plugs can cause several noticeable problems in your 1985-1991 GMC Safari. If you experience any of these issues, it might be time for a replacement.
- Rough Idling: The engine may shake or vibrate when the van is stopped.
- Trouble Starting: The engine may take longer to start or fail to start completely.
- Poor Fuel Economy: You might notice you're filling up the gas tank more often. Worn plugs lead to incomplete fuel combustion.
- Engine Misfires: You may feel a hesitation or stumble during acceleration. This can also trigger the 'Check Engine' light on later models.
- Reduced Power: The van may feel sluggish and have trouble getting up to speed.
Choosing the Right Aftermarket Spark Plugs
For a vehicle like the 1985-1991 GMC Safari, you have many excellent aftermarket spark plug options. The original equipment (OEM) brand is ACDelco, which is always a safe and reliable choice. However, other brands offer comparable or even better performance, often at a great price.
Aftermarket Brand Tiers
| Tier | Brands | Notes |
|---|---|---|
| OEM & Premium Aftermarket | ACDelco, NGK, Denso | ACDelco is the original GM parts supplier and a top choice for reliability. NGK and Denso are highly respected Japanese brands known for quality and longevity; in fact, NGK often manufactures plugs for ACDelco. These brands often feature iridium or platinum tips for longer life. |
| Quality Aftermarket | Bosch, Champion, Autolite | These are well-known brands that offer a good balance of performance and value. Bosch is a respected German manufacturer, while Champion and Autolite are long-standing American brands that make reliable copper plugs well-suited for the Safari's original ignition system. |
| Performance Focused | MSD, Accel | These brands are geared more towards high-performance applications. While they work in a Safari, they may be unnecessary for a stock engine and daily driving. |
A Note on Plug Materials
Your Safari's original plugs were likely standard copper plugs. These work great but have a shorter lifespan (around 25,000-30,000 miles). Modern platinum and iridium plugs can last much longer (60,000-100,000+ miles) and provide a consistent spark. For a daily driver, an upgrade to ACDelco, NGK, or Denso iridium or platinum plugs is a smart investment.
Known Issues & Installation Tips
Replacing spark plugs on the GMC Safari, especially with the 4.3L V6 engine, can be challenging due to tight spaces. The plugs closest to the firewall are notoriously difficult to reach.
- Access is Key: Many owners find it much easier to access all the spark plugs by removing the front wheels and the inner fender liners. Some plugs can be reached from under the van or from inside by removing the engine cover ('doghouse').
- Use the Right Tools: A good socket set with various extensions and a swivel adapter is essential. A dedicated spark plug socket with a rubber insert will help hold the plug securely.
- TSB for 1991 Models: GM issued a technical service bulletin (TSB 93-6D-2) for 1991 models noting that new spark plug designs had a longer ceramic insulator. This requires a deeper spark plug socket to avoid cracking the new plug during installation or removal.
- One at a Time: To avoid mixing up the firing order, replace one spark plug and wire at a time.
Common Ordering Mistake
The 1985-1991 GMC Safari was available with a 2.5L 4-cylinder engine or a 4.3L V6 engine. These engines require different spark plugs. Be sure to confirm your engine size before ordering to ensure you get the correct parts.
Frequently Asked Questions
How often should I change my spark plugs?
For standard copper plugs, every 25,000 to 30,000 miles is a good interval. If you use longer-lasting platinum or iridium plugs, you can extend that to 60,000 miles or more.
What is the correct spark plug gap for my Safari?
The correct gap is critical for performance. For the V6 and I4 engines in this era, the gap is typically 0.035 inches, but always check the vehicle's emissions sticker under the hood or a reliable repair manual for the exact specification for your engine. While many plugs come pre-gapped, it's always a good idea to verify the gap with a feeler gauge before installation.
Should I use anti-seize on the new spark plugs?
This is a topic of debate. Some plug manufacturers, like NGK, advise against it as their plugs have a special coating. If you do use it, apply a very small amount to the threads only, and be careful not to get any on the electrode. Using anti-seize can also change the amount of torque you apply, so reduce the manufacturer's torque spec by about 10-15%.
Do I need to use dielectric grease?
Yes. Applying a small amount of dielectric grease to the inside of the spark plug wire boot helps seal out moisture and makes it easier to remove the wire in the future. It does not go on the plug's threads.
Are there any recalls for spark plugs on this van?
No, there are no specific recalls from the NHTSA for spark plugs on the 1985-1991 GMC Safari. Any recalls found for this vehicle relate to other issues like seat bolts, steering gear, or brake rotors.
Technical Specifications
OEM Part Numbers: CR43TS
Engine options: 2.5L (151ci) L4, 4.3L (262ci) V6. Spark plug gap is typically 0.035 inches, but always confirm with the under-hood sticker.
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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.
- GMC Safari: