Since quite a few things can cause the spark plugs to fail (particularly on high mileage engines), sooner or later you're going to have to replace the spark plugs on your 3.9L V6 engine.
In this article you'll find out what causes them to fail, how often you should replace them, and what type of spark plugs you should use.
This article applies to the following GM vehicles equipped with the 3.9L V6 engine: 2006-2010 Chevrolet Impala, 2006-2007 Chevrolet Malibu, 2006-2008 Chevrolet Uplander, 2006-2009 Pontiac G6, and 2006-2009 Pontiac Montana.
Contents of this tutorial at a glance:
You can find this tutorial in Spanish here: ¿Cuando Debería Reemplazar Las Bujías? (2006-2010 3.9L V6 GM) (at: autotecnico-online.com).
What Does A Spark Plug Do?
The 3.9L V6 engine has six cylinders. Each cylinder has one spark plug.
The spark plug's job is to provide the spark that will ignite the air-fuel mixture within the cylinder.
Since your 3.9L V6 equipped GM vehicle uses a 'waste spark' type ignition system, this spark jumps from the center electrode to the side electrode or vice versa.
Symptoms Of A Bad Spark Plug
The most common symptom that you're going to see when one or several spark plugs fail, is a misfire condition that will set one or more cylinder misfire trouble codes.
You'll see one or more of the following 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 rough idle condition or misfire trouble code, the engine will not be as peppy as before. Other symptoms that you're going to see are:
- Bad gas mileage.
- A heavier exhaust smell coming out of the tailpipe.
- Hesitation when you accelerate the vehicle on the road.
What Causes A Spark Plug To Stop Working?
Spark plugs can give a very long service life. But sooner or later they're going to fail. And they usually fail either because of normal wear and tear or because carbon deposits are blocking the air gap between the center and side electrode.
And once the air gap is blocked with carbon deposits, spark will not jump between the electrodes.
This type of problem, of carbon deposits blocking the air gap between the electrodes, usually only happens on high-mileage engines that are burning oil within the cylinders.
You can tell these engines apart because they burn oil and have blue smoke coming out of their tailpipe. Another thing is that engine oil has to be added to these engines on a weekly basis.
Which Spark Plugs Should I Buy?
Your 3.9L V6 equipped vehicle comes equipped with AC Delco spark plugs and these are the spark plugs you should use (when it's time to replace them).
The AC Delco spark plug brand is the factory original spark plug that all GM vehicles use. Of course any brand of spark plugs that are specifically designed to work in your particular vehicle will work just fine.
Of course, some will work better than others. The important thing to keep in mind when replacing the spark plugs on your vehicle with after-market ones, is that they should be platinum type spark plugs and not copper spark plugs.
Should I Use 100,000 Mile Spark Plugs?
Spark plugs that are advertised as having a service life up to 100,000 miles have platinum or iridium tipped electrodes. Regular spark plugs, which have copper electrodes, do not last that long.
If you're buying the original AC Delco spark plugs to install in your 3.9L V6 engine, then these are 100,000 miles spark plugs.
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 got a high mileage engine that is burning 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
As mentioned before, the spark plugs on your 3.9L V6 engine are going to need to be replaced sooner or later. When they do need to be replaced, keep in mind the following tips and suggestions:
TIP 1: Replace the spark plugs with a completely cold engine. This is a very important suggestion because you run the risk of damaging the spark plug threads of the spark plug holes by replacing them with a hot engine.
Stripping the threads of the spark plug holes is a nightmare that you can easily avoid by removing the spark plugs with a cold engine.
TIP 2: Check the air gap of the new spark plugs with a spark plug gapper. There's a good chance that your brand new spark plugs are billed as being pre gapped. If I were you I would still check the air gap just to make sure that it isn't closed.
The one thing to keep in mind when checking the air gap on pre-gapped spark plugs is to do it very gently with the spark plug gapper. If you use too much force, you could damage the platinum or iridium tips of the center and side electrodes.
If the spark plugs you're using are not billed as being pre-gapped, then you should definitely check their air gap with a spark plug gapper.
Here are the spark plug gap specifications:
- 2006-2010 3.9L Chevrolet Impala: 0.044".
- 2006-2007 3.9L Chevrolet Malibu: 0.044".
- 2006-2008 3.9L Chevrolet Uplander: 0.044".
- 2006-2009 3.9L Pontiac G6: 0.044".
- 2006-2009 3.9L Pontiac Montana: 0.044".
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.
The torque specification of the spark plugs on the 3.9L V6 engine is: 11 ft.lbs.
More 3.9L V6 Test Tutorials
You can find a complete list of 3.9L V6 diagnostic test tutorials here: GM 3.9L Index of Articles.
Here's a list of articles you'll find there:
- How To Test The Engine Compression (2006-2010 3.9L V6 Engine).
- How To Test A Blown Head Gasket (2006-2010 3.9L V6 Engine).
- Ignition System Wiring Diagram (2006-2009 3.9L Chevrolet Impala).
- Ignition System Wiring Diagram (2006-2007 3.9L Chevrolet Malibu).
If this info really saved the day, buy me a beer!