How To Test Engine Compression (2002-2009 2.4L Honda CR-V)

Testing compression on your 2002-2009 2.4L Honda CR-V is pretty easy. What makes this test a breeze, is the fact that removing the spark plugs is a piece of cake.

In this tutorial, I'll explain the engine compression test and more importantly, how to interpret your test results so that you can find out if you have any compression issues causing a misfire or a no-start problem.

You can find this tutorial in Spanish here: Cómo Probar La Compresión Del Motor (2002-2009 2.4L Honda CR-V) (at: autotecnico-online.com).

Symptoms Of Low Or No Cylinder Compression

For the most part engine compression problems fall into one of two categories.

In the first category, engine compression problems cause the engine in your 2.4L Honda CR-V to not start. This is usually the result of 0 PSI compression on all 4 cylinders.

In the second category, the engine runs, but it runs with a misfire due to low compression values in one or more cylinders.

Here are some of the symptoms you may see when your Honda CR-V has engine compression problems:

• Engine cranks but does not start (0 compression in all cylinders).
• Blue smoke coming out of the tailpipe.
• Rough idle (engine misfires).
• Bad gas mileage.
• Engine 'misses' at idle but 'miss' disappears as you accelerate.
• Check engine light is illuminated with a MAP sensor trouble code (even tho' the MAP sensor is good).
• Misfire trouble codes set in the computer's memory: P0300, P0301, P0302, P0303, or P0304.

With this info under our belts, let's head down to the next subheading and get testing.

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 some recommendations to you:

TEST 1: Dry Compression Test

In this first test, we're gonna' test the compression of all four cylinders.

Once we have the values down, in the next section, we're gonna' see which of those cylinders we can consider to be dead and causing a problem.

NOTE: It's very important that you remove the spark plugs from a completely cold engine. If you remove the spark plugs from a hot engine, you risk damaging the threads in the spark plug holes (in the cylinder head).

OK, these are the test steps:

1. 1

   Remove the ignition coils sitting on top of the spark plugs.

2. 2

   Remove the spark plugs from a cold engine.
   
   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 plugs porcelain insulator crack and then you'll have a misfire on your hands.

3. 3

   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.

4. 4

   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 3 cylinders.

Let's take a look at what your test results mean:

CASE 1: You got 0 PSI compression on all 4 cylinders. This test result is usually the result of mechanical damage in the engine.

The most likely cause are:

• Timing belt problem.
• Blown head gasket.
• Blown engine.

Any compression value below 100 PSI (even if it doesn't go down to 0 PSI) means internal mechanical engine trouble.

CASE 2: You got uneven compression values between engine cylinders. The next step is to find out if any of those values is too low and causing a problem.

To find out, go to: Interpreting The Compression Test Results.

Interpreting The Compression Test Results

Interpreting the compression test results is easier than you think. It does require doing a little math, but I'll walk you through the entire process.

Before we jump into figuring out if the compression readings are normal or not, I'll tell you that it's normal for the compression value of each cylinder to vary somewhat.

This is due to the fact that the cylinders don't wear out exactly the same. What isn't normal is if the values vary more than 15% of the highest compression reading.

How do you figure this out? You can find out by using my online low compression calculator here: Online Low Engine Compression Calculator or by calculating this 15% difference manually.

To understand how to figure out this 15% thing manually, let's say that my 2.4L Honda CR-V's engine produced the following compression values:

• Cylinder #1 175 PSI.
• Cylinder #2 165 PSI.
• Cylinder #3 160 PSI.
• Cylinder #4 120 PSI.

The next step is to do the following math:

• Multiply .15 (15%) by the highest value: 175 x 0.15. This gives us 26.25, but we'll round it out to 26.
• Next, we subtract 26 from 175: 175 - 26 = 144.
• So now we know that the lowest possible compression value is: 144 PSI.

This means that cylinder #4, which has a compression value of 120 PSI, is the one causing the misfire (P0304) because it's below the 144 PSI minimum.

Once we've found the 'dead' cylinder, the next step is to find out what's causing the low compression value. For this step, go to: TEST 2: Wet Compression Test.

TEST 2: Wet Compression Test

Now that you've found the dead cylinder (or cylinders with low compression), the next step is to find out what's provoking the problem. Low compression in any given cylinder, is usually due to one of two things.

Either the dead cylinder's piston rings are severely worn or its cylinder head valves are severely worn.

This is where a 'wet' compression test comes in handy and it's the test we're about to do in this test section.

OK, this is what you'll need to do:

1. 1

   Add a tablespoon (or two) of engine oil in the cylinder you need to retest.
   
   I suggest using a small and long funnel so that the oil will reach the inside of the cylinder.

2. 2

   Once you've added the oil, install the compression gauge, and as before just hand tighten it.

3. 3

   Now, have your helper crank the engine till the needle stops climbing on the compression gauge.

4. 4

   You'll see one of two results:
   
   1.) The needle will climb higher than the previous compression number you recorded for this specific cylinder.
   
   2.) The needle will not move at all or stay at the same number you recorded earlier.
   
   What ever value your compression tester reads, write it down again.

5. 5

   If you have another cylinder that needs to be tested, repeat steps 1 thru' 4 on it now.

Let's take a look at what your compression test results mean:

CASE 1: The compression value shot up for the low compression cylinder. This test result lets you know that extremely worn piston rings are the ones causing the low compression value in that specific cylinder.

The reason the compression value shot up is due to the fact that the motor oil you just added helped the piston rings to create a tighter seal. This type of test result only happens when the problem is due to worn piston rings.

CASE 2: Your compression value DID NOT shoot up (stayed the same). This test result lets you know that that cylinder's cylinder head valves are worn/damaged and are the ones causing the low compression value in that specific cylinder.

More 2.4L Honda CR-V Tutorials

You can find a complete list of tutorials here: Honda 2.4L Index Of Articles.

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

• How To Test For A Blown Head Gasket (2.4L Honda CR-V).
• How To Test The TPS (2002-2004 2.4L Honda CR-V).
• How To Test Engine Compression (2002-2009 2.4L Honda CR-V).
• How To Test The MAP Sensor (2002-2004 2.4L Honda CR-V).