How To Test Engine Compression (Honda 2.2L, 2.3L)

Testing the engine compression, and more importantly knowing how to interpret the results of an engine compression test, is one of the most important diagnostic tools that you need to have in your tool box of know-how. This article will walk you thru' the compression test done on Honda 2.2L and 2.3L 4 cylinder equipped vehicles.

Why do an engine compression test? Because sometimes you run into a rough idle or misfire condition (and if your vehicle is OBD II equipped, you'll probably see one of the following misfire diagnostic trouble codes: P0300, P0301, P0302, P0303, or P0304) that no matter what gets replaced, the vehicle continues to misfire or run rough. This is were the engine compression test comes in to maybe save the day.

You can find this tutorial in Spanish here: Cómo Verificar La Compresión Del Motor (Honda 2.2L, 2.3L) (at: autotecnico-online.com).

Symptoms Of Low Or No Engine Compression

Two of the most common symptoms of low engine compression are:

• Misfire Condition (engine miss, rough idle condition).
  • Usually caused by very low compression in one cylinder.
  • Or uneven engine compression that varies more than 15% across all four cylinders.
• Cranks but Does Not Start Condition.
  • Usually caused by no compression on 2 or all 4 cylinders.

I'll go into some detail about these two in the next couple of paragraphs.

Having low or no engine compression in one cylinder on your 2.2L or 2.3L Honda 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) and your Honda vehicle is OBD II equipped (1996+), 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.

If your Honda vehicle is NOT OBD II equipped, you won't have any codes lighting up the check engine light, but you'll definitely feel a rough idle condition.

The next common scenario is having low or no engine compression on two ADJACENT engine cylinders and your Honda won't start. It'll crank but not start. This usually indicates that the head gasket has burned between the two cylinders.

If a blown head gasket is a concern, take a look at this tutorial I've written: How To Test For A Blown Head Gasket (Honda 2.2L, 2.3L).

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

1. The engine cranks very fast and this fast cranking speed is very noticeable.
2. The ignition system is sparking all 4 spark plugs, so you know it's not an ignition system problem/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. Fuel pump is working and providing pressure.
5. The most common causes of this scenario, are:
   • Blown head gasket.
   • Broken timing belt.
   • Engine thru' a rod.

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 three recommendations to you:

The 'Dry' Engine Compression Test

Let's jump right into the engine compression test.

Before you start, let me just say 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. Now, if it turns out that one or several cylinders, on your Honda, do have low or no compression, the next step would be to do a 'Wet' engine compression test (and I'll show how to do one too).

NOTE: The engine's temperature is an important consideration before you start the engine compression test. What I mean is this, the engine can not be completely cold, yet it can't be hot. It should be warmed up. Now, if you're doing this test because your car doesn't start, then don't worry about the engine being warm.

Alright, let's start:

1. 1

   Disconnect all four fuel injectors from their electrical connectors. This will prevent fuel from being injected into the cylinders as you crank the engine.

2. 2

   Disconnect the distributor from its electrical connectors. This will prevent the ignition coil from firing off spark to the spark plug wires.

3. 3

   Disconnect the spark plug wires from the spark plugs.
   
   NOTE: Before you disconnect the spark plug wires, label them with the cylinder number they belong to.

4. 4

   Remove all four spark plugs.
   
   As you're 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!

5. 5

   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.

6. 6

   Have a helper crank up your Honda as you observe the needle on the compression tester's gauge.

7. 7

   Once the needle on the gauge stops climbing, have your helper stop cranking the engine.
   
   Record this compression reading on a piece of paper. Include the number of the cylinder this reading belongs to.

8. 8

   Now repeat steps 1 thru' 6 on the other 3 cylinders.

Let's interpret your test results:

CASE 1: Low or no compression in two or ALL cylinders. This tells you you've got serious engine mechanical problems.

The most common issues would be:

• Blown head gasket.
  • To further test this, I recommend the following tutorial: How To Test For A Blown Head Gasket (Honda 2.2L, 2.3L).
• Broken timing belt.
  • To further test this, I recommend the following tutorial: How To Test For A Broken Timing Belt (Honda 2.2L, 2.3L).
• Engine thru' a rod.

CASE 2: One or two cylinders are producing a low compression value. Up to a certain point this could be normal, but if the value is too low you'll have a rough idle or misfire problem on your hands.

The next step is to do some math to find out if this low compression value is within a normal parameter or not. Go to: Interpreting Your Compression Test Results.

Interpreting Your Compression Test Results

It's not unusual to see some variation in the compression readings, especially on older high-mileage engines.

If the low compression values are small enough, you won't notice any engine performance problems.

But if the low compression values are lower than a specific range, you'll see a misfire problem or a rough idle problem.

The cool thing is that you can easily find out if the low compression values are causing an engine performance problem or not.

To find out, you'll need to figure out if the low compression values are lower than 15% of the highest compression value you got.

You can do this (figuring out the 15%) in one of two ways: You can calculate this 15% difference with pen and paper or you can use my low compression calculator. You can find the low compression calculator here: Online Low Engine Compression Calculator (at: easyautodiagnostics.com).

If you want to manually calculate the 15% difference, here's what you'll need to do:

• STEP 1: Multiply the highest compression value by 0.15 (this is the decimal value of 15%).
• STEP 2: Round the result to the nearest one (for example: 25.6 would become 26).
• STEP 3: Subtract the result (the number that was rounded) from the highest compression value.
• ANSWER: The result of this subtraction is the lowest possible compression value any cylinder can have.

Now, let me give you a more specific example: Let's say that I got the following compression readings:

Cylinder	Pressure
#1	165 PSI
#2	95 PSI
#3	155 PSI
#4	175 PSI

My next step is to do the following calculation:

• STEP 1:  175 x 0.15 = 26.25.
• STEP 2:  26.25 = 26 (rounded to nearest one).
• STEP 3:  175 - 26 = 149.
• ANSWER:  149 PSI. Any cylinder with this compression (or lower) value will misfire.

Since cylinder #2 is only producing 95 PSI, I can now conclude that it's 'dead' and causing a misfire.

To find out if the lowest compression value you got from your engine compression test is within a good range, you'll need to do the same calculation. Of course, you'll need to use the highest compression value you got and not the one in the example.

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

'Wet' Engine Compression Test

You might be asking yourself, “what's a wet compression test?” This is a variation of the same compression test you did in the previous page.

The difference being that you're gonna' add about two tablespoons of oil to the engine cylinder that showed a low compression reading in the 'Dry' compression test.

The oil that you're gonna' add to the cylinder will help determine if the low cylinder pressure or pressures you recorded in the 'Dry' compression test are caused by worn piston rings or worn cylinder head valves.

Depending on whether the compression pressure rises (on your compression tester) or not, you'll be able to say that the problem lies in the piston's rings or in the cylinder head valves.

OK, this is what you need to do:

1. 1

   Add a small amount of engine oil to the cylinder that reported low compression or no compression in the 'Dry' compression test.
   
   The amount should be about 1 to 2 tablespoons of oil.

2. 2

   Install the compression tester onto the cylinder.
   
   Do not use any type of tool to tightened the compression tester. Hand tight is fine.

3. 3

   When all is set up, have your helper crank the engine.

4. 4

   You'll get one of two results:
   
   1.) The compression value will go up (from the one you recorded before).
   
   2.) The compression value will stay the same.

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

CASE 1: The compression value shot up. This tells you that the piston compression rings are worn out and thus the problem is in the bottom end (block) of the engine in your 2.2L or 2.3L Honda.

CASE 2: The compression value stayed the same. This confirms that the problem is in the cylinder head valves.

Related Test Articles

You can find all of the 2.2L, 2.3L Honda articles here: Honda 2.2L, 2.3L Index Of Articles.

If you need and/or want to test the distributor ignition system to see if it's the source of the misfire condition (or misfire code: P0300, P0301, P0302, P03030, P0304), you can go to this link (found at easyautodiagnostics. Com): How To Test The Accord, Civic and Odyssey Distributor Type Ignition System.