How To Test Engine Compression (1992-2006 3.0L V6 Toyota Camry)

Performing an engine compression test on the 3.0L V6 Toyota Camry is not a task for the faint of heart.

This is because the upper intake manifold plenum must be removed to access cylinders 1, 3, and 5, which are located underneath it.

While the compression test is a bit challenging, it's definitely doable. In this tutorial, I'll explain how to do it and how to interpret the results.

With your test results, you'll know if low compression in one or more cylinders is behind a misfire or a misfire diagnostic trouble code. You'll also learn how to determine if an engine compression issue is causing a no-start condition.

APPLIES TO: This tutorial applies to the following vehicles:

• 3.0L Toyota Camry: 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006.
• 3.0L Toyota Avalon: 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004.
• 3.0L Toyota Sienna: 1998, 1999, 2000, 2001, 2002, 2003.
• 3.0L Toyota Solara: 1999, 2000, 2001, 2002, 2003.

Important Tips And Suggestions

TIP 1: You'll be working around a cranking engine so make safety a priority! Use common sense and stay alert at all times.

TIP 2: The cylinder head on your 3.0L Toyota Camry is made of aluminum, so never remove the spark plugs when the engine is hot (hot = normal operating temperature). Doing so can damage the spark plug hole threads in the aluminum cylinder head.

TIP 3: If you find oil in the spark plug tubes or notice that the spark plug boots are soaked with oil, it's a sign that the valve cover gaskets need to be replaced. This oil leakage may already be causing a misfire in that cylinder.

TIP 4: To test cylinders 1, 3, and 5, you'll need to remove the upper intake manifold plenum. If you've never done this before, I recommend consulting a repair manual for detailed step-by-step instructions.

Before you begin, I also suggest taking a look at this section: Precautions To Take When Removing The Intake Manifold Plenum.

Symptoms Of Low Or No Cylinder Compression

Engine compression issues usually cause one of two problems:

1. A misfiring cylinder, causing a rough idle when the engine is running.
2. An engine that cranks but won't start.

Let's break these down:

1. Rough idle (misfire) due to low compression
   • Low compression in one or two cylinders can lead to a rough idle or noticeable shaking in your 3.0L Toyota Camry. This problem often becomes less noticeable when you accelerate.
   • If your Camry is equipped with OBD II, the PCM may record one or more of the following misfire codes:
     • 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
   • NOTE: Keep in mind that the PCM doesn't always detect and log a misfire code, even when one or more cylinders have low compression.
2. Engine cranks but does not start
   • If three or more cylinders have zero compression, your engine might crank but won't start. When all six cylinders lack compression, you'll notice the following:
     • Faster cranking speed: The engine turns over much faster than normal, signaling a serious issue.
     • Spark is present: Each cylinder is receiving spark, which rules out problems with the ignition system.
     • Fuel is being delivered: The injectors are supplying fuel to the cylinders.
       • To verify this, you can use a Noid light to check for an injector pulse.
       • Alternatively, you can remove the spark plugs and check if they're soaked in fuel.
   • Zero compression across all six cylinders is usually caused by one of these issues:
     • A blown head gasket.
     • A broken timing belt.
     • The engine has thrown a rod.

With this overview of the types of compression issues, let's get started with 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 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 Compression Test

The spark plugs for cylinders 1, 3, and 5 are located under the intake manifold plenum. To access and remove them, you'll need to remove the plenum.

Before you begin removing the intake manifold plenum, take a look at the important precautions in this section: Precautions To Take When Removing The Intake Manifold Plenum.

While removing the spark plug wires and spark plugs, keep an eye out for signs of oil leaks. It's not uncommon to find spark plug tubes filled with engine oil or spark plug wire boots soaked in oil due to a leaking valve cover gasket.

If you notice this, it's likely causing the cylinder misfire issue you're troubleshooting. Replacing the valve cover gasket will be necessary to fully resolve the issue.

CAUTION: Be careful and be alert at all times since you'll be working around a cranking engine.

NOTE: If your Toyota's engine is hot, wait for it to cool down before removing the spark plugs. Removing the spark plugs from a hot engine can damage the spark plug threads in the cylinder head.

Alright, these are the test steps:

1. 1

   Disable the ignition system (1992-1993 with ignition distributors) by disconnecting the ignition coil from its electrical connector.
   
   This will prevent the ignition coil from sparking during the test.

2. 2

   Remove the intake manifold plenum.

3. 3

   Disconnect the fuel injectors from their electrical connectors.
   
   This will prevent the fuel injectors from injecting fuel during the test.

4. 4

   Remove the spark plugs.
   
   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.

5. 5

   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.

6. 6

   Have your helper crank the engine till the needle on the compression gauge stops climbing.

7. 7

   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.

8. 8

   Repeat this test step on the remaining 5 cylinders.

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

CASE 1: You got 0 PSI compression on all 6 cylinders. This is not good and tells you that one of the following conditions exists

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

Any compression value below 100 PSI (even if it does not 0 PSI) means internal mechanical engine trouble.

CASE 2: Some, but not all, of the cylinders had a low compression value. Up to a certain point this is normal -especially if the engine has a lot of miles.

What is NOT normal is if the values vary too much. With a bit of math we can find out if the lowest compression values are normal or not. Go to: Interpreting Your Compression Test Results.

The rule of thumb is that the lowest compression value cannot vary more than 15% from the highest value you recorded. Any cylinder with a compression value lower than 15% of the highest will misfire.