How To Test Engine Compression (1996-2004 3.3L Frontier, Pathfinder, Xterra)

The engine compression test on the 3.3L Nissan Frontier, Pathfinder, or Xterra is not too difficult.

In this tutorial, I'm gonna' explain how to do the engine compression test and I'm also gonna' explain how to interpret your test results.

You'll be able to find out if your Nissan has an engine compression problem or not.

APPLIES TO: Quite a few Nissan vehicles are equipped with the 3.3L V6 engine. This tutorial applies to the following vehicles:

• 3.3L Infiniti QX-4: 1997, 1998, 1999, 2000.
• 3.3L Nissan Frontier: 1999, 2000, 2001, 2002, 2003, 2004.
• 3.3L Nissan Pathfinder: 1996, 1997, 1998, 1999, 2000.
• 3.3L Nissan Xterra: 2000, 2001, 2002, 2003, 2004.

Symptoms Of Low Or No Engine Cylinder Compression

You usually see one of two types of compression problems. Either the engine compression problem is causing the engine to crank but not start.

Or the engine compression problem is causing a rough idle or a misfire problem. In other words, the engine starts but idle rough (at a traffic light, etc) or has a cylinder misfire that lights up the check engine light with a misfire trouble code.

The following list is a list of the most common symptoms you're gonna' see when the engine has a compression problem:

• 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 cylinder misfire condition (or a rough idle condition), your 3.3L Nissan Frontier, Pathfinder, or Xterra is gonna' suffer from bad gas mileage. You're also gonna' notice a heavier exhaust smell coming out of its tailpipe. Also, since the engine is not running optimally, it's not gonna' be as peppy as it was once.

Important Tips And Suggestions

TIP 1: Do not remove the spark plugs from a hot engine. Removing the spark plugs from a hot engine can result in damage to the spark plug hole threads.

If your Nissan's engine has been running for any length of time let it cool down completely before removing the spark plugs.

One method that I have used to cool the engine down in a matter of 15-20 minutes is placing a box fan on top of it to cool it down.

TIP 2: The engine has to be cranked to test the compression, for this reason take all necessary safety precautions while working around the engine when it's being cranked.

TIP 3: Have your helper wait outside of the vehicle till you're done setting up the test. This way you'll avoid having your helper accidentally crank the engine while you're installing the compression tester.

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: Finding The Dead Cylinders

As mentioned earlier don't remove the spark plugs from your Nissan's engine if the engine is hot.

Also as you're removing the spark plugs, examine them to see if you see any obvious damage on them.

One other recommendation is to label the spark plug wires so that you can put them back in their proper places.

If you don't have a compression tester you can run down to your local auto parts store and buy or borrow one from them. If you're interested in buying one, then take a look at my recommendations here: Which Compression Tester Should I Buy?

NOTE: Disable the ignition system before doing a compression test. You can easily disable the ignition system by disconnecting the distributor from its electrical connector.

OK, these are the test steps:

1. 1

   Disable the ignition system by disconnecting the distributor from its electrical connector. This will prevent the ignition coil from sparking during the test.

2. 2

   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.

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.

5. 5

   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.

6. 6

   Repeat steps 3 through 5 on the remaining cylinders.

Let's examine your test results:

CASE 1: All six cylinders had 0 PSI. This test result tells you that the engine has an internal mechanical problem.

The most common cause of this condition is a broken timing belt.

Your next steps should be to check the condition of the timing belt. I would also recommend that you check for a blown head gasket.

CASE 2: One or more cylinders had a low compression value compared to the others. This could be normal or it could be causing a problem.

To find out the next step is do some math and see if the low compression value is lower by more than 15% of the highest compression value you got. To find a detailed explanation of this calculation go to: Interpreting The Compression Test Results.

CASE 3: All six compression values were similar and above 120 PSI. This lets you know that a compression problem is not behind the no-start or misfire problem you're trying to troubleshoot.

Interpreting The Compression Test Results

In this section, I'm gonna' explain how to interpret the compression test results you got from TEST 1.

Depending on the mileage and age of the engine it's normal for the engine compression results to vary somewhat between each other.

This is due to the fact that engine cylinders don't wear out at the exact same rate over the course of thousands of miles.

But if the variation in the values is more than 15% then you're gonna' have problems. And for the most part you're gonna' see a rough idle condition or a cylinder misfire problem.

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, I'll use the following compression test results:

• Cylinder #1 175 PSI.
• Cylinder #2 165 PSI.
• Cylinder #3 160 PSI.
• Cylinder #4 120 PSI.
• Cylinder #5 150 PSI.
• Cylinder #6 150 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 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 Engine Compression Test.

TEST 2: Wet Engine Compression Test

In this section, I'm gonna' explain how to do a wet compression test.

A wet compression test will help you pinpoint the source of the low compression value you got from a specific cylinder in TEST 1.

Usually two types of problems cause a low compression test result. Either the low compression problem will be caused by worn or damaged cylinder head valves. Or the compression problem will be caused by worn piston rings.

You and I can find out without the need to disassemble the engine. And it's done by adding a small amount of engine oil to the cylinder with the low compression value.

Then that cylinder's compression is tested again. If the compression value increases then you can conclude that the low compression problem is due to worn piston rings.

If the compression value does not increase then you can conclude that that cylinder's head valves are worn out or damaged.

These are the test steps:

1. 1

   Add 1 or 2 tablespoon 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

   Install the compression gauge on the cylinder you just added oil to.

3. 3

   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

   Repeat steps 1 thru' 4 on any other cylinder you need to check.

Let's examine your test results:

CASE 1: The compression value of the cylinder you added oil to increased. This test result tells you that the low or near 0 PSI compression value is due to worn out piston rings of that specific cylinder.

CASE 2: The compression value of the cylinder you added oil to DID NOT increase. This test result confirms that the cylinder head valves of that cylinder are worn-out or damaged.

More Nissan 3.3L V6 Tutorials

If this tutorial was helpful, check out the others I've written for the 3.3L V6 equipped Nissan vehicles. You can find a complete list of tutorials here: Nissan 3.3L Index Of Articles.

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

• Mass Air Flow (MAF) Sensor TEST 3.3L Frontier, Quest, Pathfinder, XTerra.
• How To Test The Camshaft Position Sensor (3.3L V6 Frontier, Quest, Pathfinder, Xterra).
• Power Transistor Test And Ignition Coil TEST 3.3L Nissan (1996-2004).
• Ignition System Wiring Diagram (1999-2004 3.3L Frontier And Xterra).