When Should I Replace The Spark Plugs (2.4L Cobalt, HHR, Malibu, G5, G6, Solstice)

The 2.4L four cylinder engine used in the Chevrolet Cobalt, Chevrolet Malibu, Pontiac G5, and Pontiac G6 comes equipped with 4 spark plugs.

And sooner or later they're going to need to be replaced. You might be wondering: What spark plugs should I use? When should I replace them? How often I should replace them. What does a spark plug do?

Well in this tutorial, I'm going to answer those questions and offer you some practical suggestions of when and how often you should replace them.

NOTE: This tutorial applies to the following 2.4L equipped GM vehicles:

• Chevrolet Cobalt 2.4L: 2006, 2007, 2008
• Chevrolet HHR 2.4L: 2006, 2007, 2008, 2009
• Chevrolet Malibu 2.4L: 2008, 2009, 2010, 2011, 2012
• Pontiac G5 2.4L: 2006, 2007, 2008
• Pontiac G5 GT 2.4L: 2007, 2008
• Pontiac G6 2.4L: 2006, 2007, 2008, 2009
• Pontiac Soltice 2.4L: 2006, 2007, 2008, 2009

What Does A Spark Plug Do?

In a nutshell the spark plug's job is to transmit the spark that the ignition coil creates to the inside of the cylinder it is bolted into.

This spark then ignites the air-fuel mixture inside the cylinder to push the cylinder down.

Symptoms Of A Bad Spark Plug

A spark plug that is not transmitting spark is going to cause its cylinder to misfire.

Since this cylinder is not contributing to engine power it can be considered ‘dead’.

Because the fuel injection computer is designed to monitor for engine misfires, a defective spark plug will cause the check engine light to illuminate with 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.

A misfire condition is not the only symptom you're going to see when a spark plug stops sparking, you'll see one or more of the following:

• 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?

Quite a few things can cause the spark plug to stop working. And these are:

• The spark plug is worn out. The spark plug has passed its useful service life and its center electrode and side electrode are severely worn down. This causes the air gap between them to increase to the point that spark will not jump between them.
• The spark plug's center and side electrode air gap is blocked with carbon deposits.
• The ceramic inside of a spark plug is cracked.
• The spark plug boot and the spark plugs ceramic insulator have carbon tracks on them.

Carbon tracks forming on the spark plugs, from a valve cover that's leaking engine oil into the spark plug tubes, is a common problem (especially on high mileage engines). To find out more about them, take a look at the following case study: Carbon Tracks Are A Common Cause Of Ignition Misfires.

Which Spark Plugs Should I Buy?

Your 2.4L Chevrolet Malibu (Cobalt, Pontiac G5 and G6) comes equipped with AC Delco brand spark plugs.

And these are the spark plugs you should use when it's time to replace them.

Now having said that, any spark plug brand that is made for the 2.4L Chevrolet Malibu (Cobalt, Pontiac G5 and G6) engine will work. Yup, spark plug brands like Champion, Bosch, NGK, etc., sell spark plugs that will work in your 2.4L equipped GM vehicle.

Should I Use 100,000 Mile Spark Plugs?

If you're buying the original AC Delco spark plugs to install in your 3.5L Chevy Malibu, then these are 100,000 miles spark plugs.

You might be wondering what makes a spark plug last 100,000 miles? It's the fact that they're made with platinum or iridium.

These two metals can take a tremendous amount of wear and tear from eroding effects of a spark and are mainly used on the center and side electrodes of the spark plugs.

Now the catch here is that if the engine in your 2.4L Chevrolet Malibu (Cobalt, Pontiac G5 and G6) is in perfect working condition (e.g. it's not burning oil) then you're definitely going to see somewhere around 100,000 miles on those spark plugs.

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 since carbon buildup will cause them to eventually misfire.

If you do have an engine that's burning oil, my recommendation is to buy the cheapest platinum tipped spark plug since a high end spark plug will not make much of a difference in this type of situation.

Important Tips And Suggestions

As mentioned before, the spark plugs on your 2.2L Chevrolet Malibu 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.

You can get the spark plug gap specifications for your specific vehicle at you local auto parts store by calling them on the phone or Googling it.

Here are the spark plug specs:

• Cobalt 2006-2008:
  • 0.042 in (1.06 mm)
• Malibu 2006-2008:
  • 0.042 in (1.06 mm)
• G5 2006-2008:
  • 0.042 in (1.06 mm)
• G6 2006-2008:
  • 0.042 in (1.06 mm)
• Solstice 2006-2008:
  • 0.042 in (1.06 mm)

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 for the 2.4L equipped Chevrolet Malibu (Cobalt, Pontiac G5 and G6) is: 12-15 ft.lbs.

TIP 4: Install the spark plug by hand. To be a bit more specific, you should not use any type of power tool to install the spark plugs or you run the risk of damaging the spark plug hole threads in the cylinder head.

I suggest that you start threading them (in their spark plug holes) using a 3/8" fuel hose. This will ensure that you don't cross-thread the spark plug as you're installing them.

More 2.4L Chevy And Pontiac Tutorials

You can find a complete list of 2.4L Chevy and Pontiac tutorials here: GM 2.4L Index Of Articles.

Here's a list of articles you'll find there:

• How To Test The MAP Sensor (2008-2012 2.4L Chevrolet Malibu).
• How To Test For A Blown Head Gasket (2.4L Cobalt, HHR, Malibu, G5, G6, Solstice).
• How To Do A Cylinder Balance Test (2.4L Cobalt, HHR, Malibu, G5, G6, Solstice).
• How To Test Engine Compression (2.4L Cobalt, HHR, Malibu, G5, G6, Solstice).