What Do The Spark Plugs Do? (1988-2003 4.3L V6 Chevrolet S10 Pickup, GMC S15 Pickup, GMC Sonoma)

Although the spark plug is probably the smallest component of the ignition system, it plays an outsized role in keeping your Chevy S10 pickup or GMC Sonoma's 4.3L V6 engine running optimally.

In this article, I'll answer some of the most commonly asked questions about spark plugs.

You can find this tutorial in Spanish here: La Bujía ¿Qué Es Y Para Que Sirve? (1988-2003 4.3L V6 Chevrolet S10 Pickup, GMC S15 Pickup, GMC Sonoma) (at: autotecnico-online.com).

APPLIES TO: This tutorial applies to the following vehicles:

• 4.3L V6 Chevrolet S10 Pickup: 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003.
• 4.3L V6 GMC S15 Pickup: 1988, 1989, 1990.
• 4.3L V6 GMC Sonoma: 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003.
• 4.3L V6 Isuzu Hombre: 1997, 1998, 1999, 2000.

What Does A Spark Plug Do?

The spark plug's role is to ignite the air/fuel mixture inside the cylinder it's connected to with a spark.

The spark plug creates its spark by causing the high voltage it receives (from the ignition coil) to jump from its center electrode to its side electrode.

Symptoms Of A Bad Spark Plug

A bad spark plug or spark plugs can cause various engine performance issues. The most common one is an engine cylinder misfire.

On the OBD II equipped Chevrolet S10 (GMC Sonoma), you'll see the fuel injection computer illuminate the check engine light with one of the following misfire diagnostic trouble codes:

• P0300: Random Cylinder Misfire.
• P0301: Cylinder #1 Misfire.
• P0302: Cylinder #2 Misfire.
• P0303: Cylinder #3 Misfire.
• P0304: Cylinder #4 Misfire.
• P0305: Cylinder #5 Misfire.
• P0306: Cylinder #6 Misfire.

Besides a misfire trouble code illuminating the check engine light (OBD II only), you'll see one or more of the following symptoms:

• Bad gas mileage.
• Extended engine cranking (engine takes longer than usual to start).
• A heavier-than-normal exhaust smell coming out of the tailpipe.
• The engine is not as peppy as it used to be.
• Hesitation when you accelerate the vehicle on the road.
• Fuel smell coming from the tailpipe.

What Causes A Spark Plug To Stop Working?

Quite a few different conditions and problems can cause the spark plug to fail:

• Normal wear and tear. In other words, they simply wear out.
• Carbon deposits blocking the air gap between the center and side electrodes.
• Damage caused by the installation process (for example, during a tune-up).

Carbon deposits blocking the spark plug's electrodes are usually caused by engine oil burning inside the cylinder the spark plug is connected to.

You can tell these engines apart because:

• They have blue smoke coming out of the tailpipe (when the engine is running or when under load).
• They need to have engine oil added on a regular basis.

How Do I Know My Spark Plugs Need Changing?

It's time to replace the spark plugs when one of the following conditions has been met:

• The spark plugs are showing heavy wear and tear.
• The spark plugs are causing an engine performance problem.
• You're following a recommended spark plug change interval.

Which Spark Plugs Should I Buy?

Your Chevy S10 (GMC Sonoma) came equipped with AC Delco spark plugs when it left the factory.

The AC Delco brand of spark plugs are the spark plugs that I would recommend you install in your vehicle when it comes time to replace them.

Having said that, any other brand of spark plug specifically designed for your vehicle will work.

Should I Use 100,000 Mile Spark Plugs?

Spark plugs advertised as having a service life of up to 100,000 miles have platinum or iridium-tipped electrodes. Regular spark plugs with copper electrodes do not last that long.

Now the catch here is that if the engine is in perfect working condition (e.g. It's not burning oil) then these spark plugs will give you a service life of about 100,000 miles.

But if you have a high mileage engine that burns oil, you're not going to see anywhere near 100,000 miles on those spark plugs. Carbon buildup will eventually close the air gap between the spark plug electrodes and cause a misfire.

Important Tips And Suggestions

Here are a couple of important tips that will save you time (and frustration) when replacing the spark plugs:

TIP 1: Replace the spark plugs with a completely cold engine. The cylinder heads of your 4.3L V6 engine are made of aluminum, and this means that the spark plug hole threads can easily be stripped if the spark plugs are removed with a hot engine.

Stripping the spark plug hole threads in the cylinder head is a nightmare that can easily be avoided by removing the spark plugs with a completely cold engine.

TIP 2: Check the air gap of the new spark plugs with a spark plug gapper. Don't trust that the spark plugs are already pre-gapped.

I've diagnosed quite a few misfire problems that were caused by spark plugs that were advertised as being pre-gapped but were not.

TIP 3: Use a torque wrench to tighten the spark plugs. If you don't tighten the spark plugs enough you run the risk of having them come out as you're driving down the road. This could also damage the spark plug hole threads in the cylinder heads.

If you over tighten the spark plugs, then you run the risk of damaging the threads of the spark plug hole.

The way to avoid any of these problems is to use a torque wrench to tighten the spark plugs. Now, it's easier said than done because some of the spark plugs are in very tight places and it can be challenging to use a torque wrench on them. Still, you won't go wrong if you use a torque wrench.