Interpreting The Results Of The Engine Compression Test
CASE 1: Low or no compression in 2 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: Low or no compression in one cylinder. The idea behind the engine compression test (in the case of a misfire condition or rough idle condition) is to find out if any one engine cylinder is not contributing 100% of its power to the overall engine output. If only one cylinder has lower than normal compression, your Honda will run rough or cause a misfire code to set and turn on the check engine light.
So then, to wrap things up, the individual cylinder compression readings of each engine cylinder can not vary more than 15% and this is how you can find out:
Grab a calculator and multiply the highest compression reading that you recorded by 0.15.
So, let's say that cylinder #4 gave you the highest reading of 170 PSI. Well 170 X 0.15 gives you 26 (25.5 rounded off).
Now, the next step is to subtract 26 from 170, which gives us 144 PSI.
So then, 144 PSI is the lowest possible compression reading that any one of the rest of the engine cylinders can have. Any compression reading below this and that engine cylinder will misfire.
Now, so that this calculation can make more sense to you, let's say that my Accord (or Odyssey or Prelude) gave me the following compression readings:
- Cylinder #1 175 PSI.
- Cylinder #2 160 PSI.
- Cylinder #3 165 PSI.
- Cylinder #4 30 PSI.
The next step is to do the math: 175 x 0.15= 26, 175-26= 149. So, now I know that cylinder #4 is the one causing the misfire!!
Now that you've found the cylinder with the low compression, the next step is to see if this low compression is caused by worn cylinder head valves or worn piston rings. For this test, 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:
- 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.
- Install the compression tester onto the cylinder.
- Do not use any type of tool to tightened the compression tester. Hand tight is fine.
- When all is set up, have your helper crank the engine.
- You'll get one of two results, either the compression value will go up (from the one you recorded before) or it will stay the same.
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.
Why An Engine Compression Test?
This is one of the most overlooked tests to find the root cause of a misfire code, rough idle or an engine miss or a blown head gasket.
Over the years, I have solved many unsolvable misfire codes, rough idle, lack of power issues by doing a simple engine compression test and if you're faced with something similar, I highly recommend doing an engine compression test.
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.
Engine Compression Gauge Testers
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!
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.
If this info saved the day, buy me a beer!