How To Test Engine Compression (Nissan 2.4L, 2.5L)

In this article, I'm gonna' show you how to do an engine compression test on your Nissan 2.4L Altima, Pathfinder or Xterra vehicle.

An engine compression test is not hard to do (since you're only dealing with 4 cylinders) and it should take you about 30 minutes to do.

Important Tips And Suggestions

TIP 1: The compression test is done with the engine cranking, so you'll need to be careful and take all necessary safety precautions.

TIP 2: You'll need a helper to crank the engine for you, while you eye-ball the compression tester. My suggestion to your helper wait outside the vehicle till you're done setting up the test. Once the test is done, ask you helper to wait outside again. This will help you to avoid having him or her accidentally crank the engine while you're setting up the test.

TIP 3: If the engine starts, you should perform the compression test with the engine warmed up, but not completely hot (normal operating temperature). If the engine does not start, don't worry about it.

Symptoms Of Low Or No Engine Compression

Having low or no engine compression in one cylinder on your 2.4L Altima (Frontier, or Xterra) will cause your engine to miss at idle and you'll definitely feel there's something wrong when you accelerate the vehicle.

When this happens (low or no compression on just one cylinder), you'll see one of the following misfire diagnostic trouble codes:

• P0300: Random Cylinder Misfire.
• P0301: Cylinder #1 Misfire.
• P0302: Cylinder #2 Misfire.
• P0303: Cylinder #3 Misfire.
• P0304: Cylinder #4 Misfire.

Now, a lot of times, low compression at idle, will only cause a Rough Idle Condition and it won't set a Misfire Trouble Code at all.

The next common scenario is having low or no engine compression on two engine cylinders and your Altima (Frontier, or Xterra) won't start. It'll crank but not start. This usually indicates a blown head gasket.

If a blown head gasket is a concern, take a look at this tutorial I've written: How To Troubleshoot A Blown Head Gasket (Nissan 2.4L, 2.5L).

When you have a situation where you have NO compression on ALL 4 cylinders, you'll see:

1. When you crank the engine over, it cranks very fast and this fast cranking speed is very noticeable.
2. You'll have spark (in every cylinder), so you know it's not an ignition system issue.
3. The fuel injectors spray fuel.
   • You can confirm this with a Noid light test.
   • Also, you can confirm this, although indirectly, by removing the spark plugs and checking to see if they are fuel soaked (fuel fouled).
4. The most common causes of this scenario, are:
   • Blown head gasket.
   • Broken timing chain.
   • Engine thru' a rod.

OK, having covered the most common scenarios of low compression and no compression, let's get testing to see if this is the case on your 2.4L Altima (Frontier, or Xterra).

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.

2) Where to buy:  You can buy an engine compression tester just about anywhere, but you'll end up paying more for it (especially at your local auto parts store). The above links will help you comparison shop. I think you'll agree it's the better way to save money on the compression tester!

TEST 1: 'Dry' Engine Compression Test

Let's jump right into the 'dry' Engine Compression Test.

Before you start, let me just say (one more time) that you'll be working around a cranking engine, so you have to be careful and stay alert at all times.

This is a pretty easy test and at the end, I'll show you how to interpret your test results. If you do find that you do have one or several engine cylinders with low compression, I recommend testing those cylinders with a 'wet' compression test (and you'll find the instructions for this 'wet' compression test in page 3 of this article).

Alright, let's start:

1. 1

   Disable the fuel system. This will prevent fuel from being injected into the cylinders as you perform the test.
   
   You can do this by disconnecting all of the fuel injectors or by removing the fuel pump relay.

2. 2

   Disable the ignition system. This will prevent the ignition coil pack from creating and delivering spark to the spark plug wires.
   
   You can accomplish this by disconnecting the distributor from its electrical connector(s).

3. 3

   Now, disconnect the spark plug wires (label them before you disconnect them) and the remove all 6 spark plugs.
   
   As your taking them out, be careful and don't drop any of them on the floor, or you could cause the spark plug's ceramic insulator to break, and this will cause a misfire!

4. 4

   Thread the engine compression gauge into the spark plug hole for the number 1 engine cylinder (this is the spark plug hole closest to the drive belt).
   
   Hand tighten the compression gauge only! Do not use any type of tool to get it tight.

5. 5

   Have your helper crank the engine.

6. 6

   When the tester's needle stops climbing, have your helper stop cranking the engine.

7. 7

   Now, at whatever number the needle, on the gauge, stops, write this number down along with the number of the cylinder.
   
   This number will be the maximum compression value for that specific cylinder.

8. 8

   Repeat steps 4-7 on the other cylinders.

Let's take a look at how to interpret your test results:

CASE 1: No compression in 2 or more cylinders. This test result tells you that the engine has serious internal problems.

The most common issues behind this test result would be:

• Broken timing chain.
• A blown head gasket.
• The engine threw a rod.

CASE 2: Low compression in one or more cylinders. To a certain point, it's normal for the compression to vary a little between cylinders (as the engine accumulates thousands of miles). But if these values vary too much, then you're gonna' have a bonafide misfire on your hands.

So, your next step is to do the math and find out if these compression values are within normal parameter or not. Go to: Interpreting Your Compression Test Results.