Common Causes Of Spark Plug Failure (1999-2004 3.4L V6 Olds Alero)

The spark plug —such a small component— but it's probably one of the hardest-working parts that helps get the engine started and keep it running.

Each time you crank and start the engine, it has to fire thousands of times per minute to ignite the compressed air/fuel mixture in the cylinder it's connected to.

In this tutorial, I'm going to show you the most common reasons why spark plugs fail on the 3.4L V6 Oldsmobile Alero. We'll cover the most common types of spark plug failure, like normal wear, carbon fouling, and oil fouling, and I'll explain what each one tells you about what's going on inside the engine.

One of the neat things about inspecting a used spark plug is that it can give you some valuable clues about the condition of the engine. By the end of this guide, you'll know what to look for, when it's time to replace your spark plugs, and which type of spark plug is your best bet if your 3.4L V6 is burning engine oil.

APPLIES TO: This tutorial applies to the following vehicles:

• 3.8L V6 Buick LeSabre: 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005.

Why Spark Plugs Wear Out On High-Mileage Engines

No spark plug lasts forever. Every time the spark plug fires, a tiny amount of material is worn away from the center and Ground electrodes. You can't see it happening from one engine start to the next, but after thousands upon thousands of sparks, that wear becomes significant.

As the electrodes wear down, the spark plug gap gets larger. The larger that gap becomes, the harder the ignition coil has to work to fire the spark plug. Eventually, the spark isn't as strong or as consistent as it should be, and that's when performance problems begin to show up.

How long a spark plug lasts depends mostly on the type that's installed. In general, you can expect something along these lines:

• Copper spark plugs: Usually provide reliable service for about 50,000 to 60,000 miles.
• Platinum spark plugs: Under normal driving conditions, they commonly last close to 100,000 miles.

Those mileage figures assume the engine is in good mechanical condition. If your 3.4L V6 Oldsmobile Alero is burning engine oil, don't expect the spark plugs to last anywhere near that long.

When engine oil gets into the combustion chamber and burns, it leaves behind carbon deposits that slowly build up on the spark plug tip. Sooner or later, those deposits interfere with the spark, and the affected cylinder begins to misfire.

When that happens, you're usually going to notice one or more of these symptoms:

• Rough idle: The engine idles rough and may shake more than usual.
• Lack of power: The engine doesn't accelerate or pull as well as it normally does.
• Bad gas mileage: Fuel mileage drops because one or more cylinders aren't burning the air/fuel mixture efficiently.

Since a failed spark plug will cause the engine to misfire, the PCM will usually detect the misfire, turn on the check engine light and store one or more of the following misfire trouble codes in its memory:

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

When Should You Replace The Spark Plugs?

There's no single answer to this question because it depends on the condition of your engine. The first thing you need to ask yourself is:

Is your 3.4L V6 burning engine oil?

If it isn't, then life is pretty easy. Just replace the spark plugs at the interval recommended by Oldsmobile in the owner's manual or service manual.

If the engine is burning oil, that's a different story. As the oil burns inside the combustion chamber, it leaves behind carbon deposits that collect on the spark plug tip. Those deposits eventually interfere with the spark plug's ability to fire properly and can cause a rough idle or a cylinder misfire long before the spark plugs reach their normal service life.

If your engine is burning oil, these are the most common signs that it's time to replace the spark plugs:

• Rough idle or cylinder misfire: The engine suddenly begins idling rough or develops one or more misfiring cylinders.
• Check engine light: The PCM detects the misfire, stores one or more misfire trouble codes, and turns on the check engine light.

If you're not sure whether the engine is burning oil, here are a few telltale signs to watch for:

• Engine oil level keeps dropping: You find yourself adding engine oil between oil changes.
• Blue smoke during acceleration: Blue exhaust smoke comes out of the tailpipe when you step on the accelerator.
• Blue smoke when you first start the engine: A puff of blue smoke comes out of the tailpipe after the engine has been sitting for several hours or overnight.

If your 3.4L V6 isn't burning engine oil, you can generally expect the spark plugs to last about this long:

• Copper spark plugs (OEM type): About 50,000 to 60,000 miles.
• Platinum spark plugs: Under normal driving conditions, about 100,000 miles.

Which Spark Plugs Should You Buy?

If you're wondering whether you should buy ACDelco spark plugs or go with another brand, here's my take on it. As long as you're buying a quality spark plug from a well-known manufacturer, you're going to be just fine.

Your 3.4L V6 Oldsmobile Alero came from the factory with ACDelco copper spark plugs, and they're always an excellent choice. But NGK, Autolite, Bosch, and several other reputable brands also make high-quality spark plugs that work just as well.

The more important question isn't which brand to buy. It's whether or not your engine is burning oil.

If the engine is burning oil, it won't matter whether you install copper, platinum, or iridium spark plugs. The oil burning inside the combustion chambers is eventually going to leave carbon deposits on the spark plug tips, and those deposits are going to cause the spark plugs to carbon foul.

Because of that, I usually recommend installing a good-quality set of copper spark plugs on an engine that's burning oil. They're less expensive, and since they're eventually going to carbon foul anyway, there's really no advantage to spending extra money on platinum or iridium plugs.

If the engine isn't burning oil, then you've got more options. You can install another set of OEM-style copper spark plugs or step up to platinum spark plugs if you'd like the longer service life. Either way, you're making a good choice.

So here's the rule of thumb I follow:

• The engine is burning oil: Install a quality set of copper spark plugs and save your money. Premium spark plugs aren't going to last any longer once they start getting coated with oil deposits.
• The engine isn't burning oil: Go with OEM-style copper spark plugs or upgrade to platinum spark plugs if you want the longer maintenance interval. Both are excellent choices.

Other Things That Can Cause A Spark Plug To Fail

Normal wear and carbon fouling are probably the most common reasons a spark plug stops doing its job, but they're certainly not the only ones. Quite a few engine and ignition system problems can keep it from firing properly.

When that happens, the result is usually pretty obvious. The affected cylinder begins to misfire, the engine starts running rough, and in many cases, the check engine light comes on.

Here are some of the more common problems I've seen over the years that can foul or damage a spark plug:

• Leaking fuel injector: A leaking or stuck-open fuel injector can flood the cylinder with too much fuel and foul the spark plug.
• Bad spark plug wire: A damaged or worn-out spark plug wire can keep the spark from ever reaching the spark plug.
• Failed ignition coil: A bad ignition coil won't be able to supply spark to one or more cylinders.
• Low engine compression: A cylinder with low compression can't burn the air/fuel mixture efficiently, which eventually leads to a carbon-fouled spark plug.
• Engine burning oil: Oil entering the combustion chamber leaves deposits on the spark plug that eventually interfere with the spark and cause a misfire.

I've also seen plenty of brand-new spark plugs get damaged before the engine was ever started. Most of the time, it comes down to one of these installation mistakes:

• Cracking the porcelain during installation: Sometimes the porcelain gets cracked while the spark plug is being installed. When it happens, that cylinder will misfire.
• Dropping the spark plug: Even a small drop can crack the porcelain or close the air gap between the electrodes.
• Accidentally changing the spark plug gap: Bumping or mishandling the spark plug can bend the Ground electrode and change the air gap.
• Not checking the spark plug gap before installation: Even if the spark plug comes pre-gapped, it's always worth taking a few seconds to make sure the gap matches your engine's specifications.
• Thermal shock: This usually happens when someone power washes a hot engine. The cold water can crack the spark plug's porcelain insulator.

REAL-WORLD CASE STUDIES:

Over the years, I've diagnosed plenty of engines with spark plug problems that turned out to be caused by something else. I've also dealt with carbon-fouled spark plugs, installation mistakes, oil-burning engines, and low-compression cylinders. I've written about many of those real-world repairs, and you can check them out here:

• Diagnosing A Toyota Corolla Misfire Case Study —a misfire caused by a simple installation error.

• Troubleshooting A Hard To Diagnose Misfire Case Study (GM 3.1L, 3.4L) —this one involved low compression causing a stubborn cylinder misfire (it was my brother-in-law's car, too).

• Carbon Tracks Are A Common Cause Of Ignition Misfires —spark plug and spark plug wire boot with carbon tracks causing a cylinder misfire (at: easyautodiagnostics.com).

More 3.4L V6 Oldsmobile Alero Diagnostic Tutorials

You can find a complete list of diagnostics tutorials for your 3.4L V6 Oldsmobile Alero in this index:

• 3.4L V6 Oldsmobile Alero Index of Articles.

Here's a small sample of the tutorials you'll find:

• How To Test The TPS With A Multimeter (1999-2004 3.4L V6 Oldsmobile Alero).
• How To Test The 7X Crankshaft Position Sensor (1994-2004 3.4L V6 Olds Alero).
• How To Test For A Blown Head Gasket (1999-2004 3.4L V6 Olds Alero).
• How To Test Engine Compression (1999-2004 3.4L V6 Oldsmobile Alero).