In this tutorial I'm going to show you how to test the engine compression on the 2.4L engine used in the Chevrolet Cobalt, Chevrolet Malibu, Pontiac G5, Pontiac G6.
With the help of this tutorial you'll be able to find out if an engine compression problem is causing your vehicle to not start or if it's behind a misfire problem that's lighting up the check engine light.
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
Contents of this tutorial at a glance:
Symptoms Of Low Or No Engine Cylinder Compression
For the most part you're going to see one of two types of problems when the engine is suffering a compression problem.
The most common type of problem you're going to see with a compression problem is low compression in one or two cylinders that's causing the engine to misfire or idle rough.
In this case you'll see one or more of the following symptoms:
- Misfire trouble codes:
- P0300: Random Cylinder Misfire.
- P0301: Cylinder #1 Misfire.
- P0302: Cylinder #2 Misfire.
- P0303: Cylinder #3 Misfire.
- P0304: Cylinder #4 Misfire.
- Blue smoke coming out of the tailpipe.
- Rough engine idle that disappears when you accelerate the engine.
- Bad fuel mileage.
The other type of compression problem is one that causes the engine to not start. To be a bit more specific the engine is going to crank but not start.
Which Compression Tester Should I Buy?
There are lot of engine compression testers to choose from and many places to buy them. I'm gonna' make two recommendations to you:
1) Which one to buy: The engine compression tester that I have always used is the Actron CP7827 Compression Tester Kit. My only complaint about this engine compression tester is that it does not come with a case to store it in.
Engine Compression Gauge Testers
TEST 1: Finding The Dead Cylinders
OK to get started we're going to test the compression of all four cylinders.
What makes testing the engine compression easy on the 2.4L engine is that removing the spark plugs is a breeze.
Once you have tested the compression of all four cylinders, then we'll move on to the next section which is interpreting the results of your compression test.
If you don't have a compression tester, you can borrow one from your local auto parts store or you can buy one Online. Check out my recommendations here: Which Compression Tester Should I Buy?
IMPORTANT: If the engine has been running for any length of time then let it cool down completely. Never remove the spark plugs from a hot engine or you run the risk of damaging the spark plug hole threads in the cylinder head.
OK, these are the test steps:
Disable the ignition system by disconnecting the ignition coil pack from its electrical connectors. This will prevent the ignition coil from sparking during the test.
Remove the spark plugs. Remember, the engine can not be hot!
When removing the spark plugs, be careful not to drop any of them on the floor, or you run the risk of having the spark plug's porcelain insulator crack and then you'll have a misfire on your hands.
Thread the engine compression gauge into the spark plug hole for the number 1 engine cylinder. Hand tighten the compression gauge only! Do not use any type of tool to get it tight.
Have your helper crank the engine till the needle on the compression gauge stops climbing.
Now, record on paper the value at which the needle stopped and the number of the engine cylinder on a piece of paper. Release the pressure on the gauge and repeat this step one more time.
Repeat this test step on the remaining cylinders.
Let's examine your test results:
CASE 1: One or two cylinders had a much lower compression value than the others. This could be normal or it could be a problem.
To find out if these low engine compression values are causing an engine performance issue, go to: Interpreting The Compression Test Results.
CASE 2: Three or more cylinders had almost no compression or 0 PSI compression. The engine is not gonna' start with this type of compression test result and usually indicates a severe internal engine problem.
I recommend doing a wet compression test on these cylinders to find out if the problem is in the block or cylinder head. Go to: TEST 2: Wet Engine Compression Test.
CASE 3: The compression value of all 4 cylinders was similar and above 120 PSI. This is the correct and expected test result.