Choosing the Right Spark Plugs for Your 1987-1991 GMC V1500 Suburban
Keep your classic Suburban's TBI engine running strong with the right set of new aftermarket spark plugs.
- For stock 1987-1991 V1500 Suburbans, standard copper spark plugs (like ACDelco R45TS) are the most cost-effective and reliable choice.
- Always verify the spark plug gap before installation; the typical gap is 0.035 inches, but check your under-hood sticker.
- While expensive iridium and platinum plugs are available, they offer little to no performance advantage on these older TBI engines.
- 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
When the spark plugs in your V1500 Suburban start to wear out, you'll likely notice a decline in how your truck drives. Because these engines are relatively straightforward, the symptoms are usually easy to spot.
- Rough Idle: The engine may shake or vibrate more than usual when you're stopped at a light.
- Poor Acceleration: You might feel the truck is sluggish or doesn't have the power it used to.
- Reduced Fuel Economy: Worn plugs can cause incomplete fuel combustion, meaning you'll be visiting the gas station more often.
- Hard Starting: The engine may crank for longer than usual before it starts, or it might not start at all.
- Engine Misfires: You may feel a hesitation or stumble during acceleration. In some cases, the "Check Engine" light may come on.
Choosing the Right Aftermarket Spark Plug
For the 1987-1991 V1500 Suburban, the original factory plugs were standard copper AC Delco plugs. While modern platinum and iridium plugs are available, many owners and mechanics find that these older TBI engines run best on the type of plug they were designed for: copper.
Brand & Material Tiers
| Tier | Brands | Plug Material | Notes |
|---|---|---|---|
| OEM / Recommended | ACDelco, NGK | Copper | ACDelco is the original equipment manufacturer. NGK is a highly-regarded alternative that many owners trust. Both are excellent choices for a stock engine. |
| Standard / Good Value | Autolite, Champion, Denso | Copper | These brands offer reliable, affordable copper plugs that work very well in these trucks. They are a great balance of performance and price. |
| Performance / Modified | MSD, Accel | Iridium / Copper | If your engine is modified with performance parts, brands like MSD and Accel offer plugs designed for higher combustion pressures and temperatures. |
| Long Life (Use with Consideration) | Bosch, Denso, NGK | Platinum / Iridium | While platinum and iridium plugs last much longer, they are more expensive and may not provide a noticeable performance benefit on a stock TBI engine. Some owners prefer to stick with the original copper design. |
A Note on Platinum and Iridium Plugs
While modern materials like platinum and iridium offer a much longer service life (60,000-100,000 miles), they don't always play well with older ignition systems. The TBI engines in these Suburbans were designed for copper plugs, which are excellent conductors of heat and electricity. For a stock, daily-driven truck, standard copper plugs changed every 20,000-30,000 miles are often the most reliable and cost-effective choice.
Known Issues, Recalls, and TSBs
For a vehicle of this age, there are no specific active recalls or Technical Service Bulletins (TSBs) from NHTSA related to spark plugs for the 1987-1991 GMC V1500 Suburban. Any issues are typically related to normal wear and tear. However, a TSB from 2003 did announce a switch from platinum to iridium tips for many GM V8 engines and a change in the recommended gap to 0.040 inches for those newer plugs. For your vehicle, it's best to stick to the original specifications unless using a modern plug that specifies a different gap.
Installation Pro-Tips
- Check the Gap: Even if plugs come "pre-gapped," always double-check the gap with a feeler gauge before installation. The correct gap for a standard plug in the 5.7L V8 is typically 0.035 inches, but always verify with your vehicle's under-hood emissions sticker.
- Use a Torque Wrench: Over-tightening can damage the cylinder head, and under-tightening can cause a leak. The correct torque is typically around 20-22 ft-lbs, but consult a service manual for your specific engine.
- Dielectric Grease: Apply a small amount of dielectric grease to the inside of the spark plug wire boot to prevent it from getting stuck on the plug's ceramic and to ensure a good seal against moisture.
- Tune-Up in a Box: When replacing spark plugs, it's a great time to also inspect or replace the spark plug wires, distributor cap, and rotor for a complete ignition system tune-up.
Frequently Asked Questions (FAQ)
How often should I change the spark plugs on my Suburban?
For standard copper plugs, a good interval is every 20,000 to 30,000 miles. If you opt for more expensive iridium or platinum plugs, they can last 60,000 miles or more, but the performance benefit on this engine is minimal.
What is the correct spark plug gap for my 1987-1991 Suburban?
For the common 5.7L V8 engine with standard copper plugs, the recommended gap is 0.035 inches. However, it is critical to check the emissions label under the hood of your specific truck, as this is the most accurate source. Some aftermarket plugs may require a different gap.
Do I need special tools to change my spark plugs?
You will need a ratchet, a spark plug socket (typically 5/8" or 16mm), a socket extension, and a torque wrench. A spark plug gap gauge is also essential for checking the gap. Spark plug wire pliers can be helpful for removing stubborn wires without damaging them.
Should I replace my spark plug wires at the same time?
It's a good idea. Spark plug wires degrade over time, leading to weak spark and misfires. Replacing the plugs, wires, distributor cap, and rotor all at once ensures your entire ignition system is refreshed and reliable.
Technical Specifications
OEM Part Numbers: R45TS (ACDelco) 19354415 (ACDelco)
Thread Size: 14mm, Seat Type: Tapered, Hex Size: 5/8" (16mm), Standard Gap: 0.035" (verify on vehicle).
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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 V1500 Suburban: