Spark Plug Replacement Guide for the 1987-1991 GMC R2500 Suburban
Keep your classic R2500 Suburban running strong with the right spark plugs and avoid common replacement mistakes.
- Stick with standard copper-core spark plugs like the AC Delco CR43TS; they are inexpensive and what your truck's engine was designed for.
- Avoid expensive platinum or iridium plugs, as they offer little to no benefit for this specific ignition system and are not worth the extra cost.
- Always check and set the spark plug gap to 0.035 inches before installation.
- Consider replacing the spark plug wires, distributor cap, and rotor at the same time for a complete ignition system tune-up.
Symptoms of Failing Spark Plugs
When the spark plugs in your R2500 Suburban begin to fail, the signs are usually straightforward. Because these trucks have relatively simple ignition systems, you'll likely notice a change in how the engine runs. Pay attention to these common symptoms as they are clear indicators that it's time for a tune-up.
Rough Idle
Your engine may shake or vibrate more than usual when you're stopped at a light. This is often caused by a worn plug failing to fire consistently.
Poor Acceleration
You might feel a hesitation or a general lack of power when you press the gas pedal. Worn plugs can't create a strong enough spark to burn the fuel mixture efficiently.
Reduced Fuel Economy
If you find yourself filling up the tank more often, failing spark plugs could be the culprit. Incomplete combustion means wasted fuel.
Hard Starting
The engine may take longer to turn over and start, especially in cold weather. A weak spark makes it difficult to initiate combustion.
Choosing the Right Aftermarket Spark Plug
For the 1987-1991 GMC R2500 Suburban, the original factory plugs were standard copper AC Delco plugs. While modern platinum and iridium plugs are available, the overwhelming consensus from owners and mechanics is that these older TBI engines run best on the simple, inexpensive copper plugs they were designed for.
Pro Tip: Stick with standard copper-core spark plugs. The factory-recommended AC Delco CR43TS is a proven, affordable choice that works perfectly with your truck's ignition system. There is little to no performance benefit from using more expensive platinum or iridium plugs on these engines.
Brand Tiers for Your Suburban
- Tier 1 (Highly Recommended): AC Delco (OEM), NGK. AC Delco is the original part and a trusted choice. NGK's V-Power or standard copper plugs are a high-quality alternative that many owners use with great success.
- Tier 2 (Good Value): Autolite, Denso, Champion. These brands offer reliable standard copper plugs that are a good value. Autolite and Champion are classic American brands that have been used in these trucks for decades.
- Tier 3 (Use with Caution): Bosch. While Bosch makes quality parts, some owners have reported compatibility issues or rougher performance with their plugs in these specific GM engines compared to OEM-style copper plugs.
| Tier | Brand Examples | Typical Price (per plug) | Lifespan (approx.) |
|---|---|---|---|
| Value (Copper) | AC Delco, NGK, Autolite, Champion | $3.53 - $6.00 | 20,000 - 30,000 miles |
| Premium (Iridium/Platinum) | NGK Iridium, Bosch, Denso Iridium | $7.00 - $22.00 | 60,000 - 100,000 miles |
| Performance | Accel, MSD | $21.00 - $80.83 | Varies |
Known Issues, Recalls, or TSBs
There are no specific recalls or Technical Service Bulletins (TSBs) from the NHTSA related to spark plugs for the 1987-1991 GMC R2500 Suburban. The ignition system is robust and straightforward, with most issues arising from normal wear and tear of maintenance items like plugs, wires, the distributor cap, and rotor.
Frequently Asked Questions (FAQ)
What is the correct spark plug gap for my Suburban?
The recommended spark plug gap for both the 5.7L and 7.4L V8 engines in this Suburban is 0.035 inches. Always verify this with a feeler gauge before installation, even if the plugs are sold as "pre-gapped."
Should I use anti-seize on the new spark plugs?
Most modern spark plug manufacturers, including NGK and ACDelco, advise against using anti-seize. Their plugs have a special plating on the threads that prevents seizing and provides proper torque readings. Using anti-seize can lead to over-tightening and potential engine damage.
Do I really need a torque wrench?
Yes. Using a torque wrench is crucial to avoid damaging the spark plug or the engine's cylinder head. Over-tightening can break the plug's ceramic insulator or strip the threads in the head, while under-tightening can lead to compression loss and misfires.
What are common mistakes when changing these spark plugs?
Common mistakes include not cleaning the area around the old plug before removal, which can let debris fall into the cylinder. Another is pulling on the spark plug wire itself instead of the boot, which can damage the wire. Also, be sure to change one plug and wire at a time to avoid mixing up the firing order.
Technical Specifications
OEM Part Numbers: CR43TS 5614029 19354425
Recommended Spark Plug: AC Delco CR43TS (or equivalent copper plug) Recommended Gap: 0.035 inches
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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 R2500 Suburban: