A manual cylinder balance test will help you find a misfiring cylinder (also known as a ‘dead’ cylinder) that's causing your 1.7L Honda Civic to idle rough.
Why perform a manual cylinder balance test? Well, there are times your Honda's PCM can't or doesn't pinpoint the misfiring cylinder.
In other words, the PCM doesn't register a specific misfire code like a: P0301, P0302, P0303 or a P0304 to let you know which cylinder is ‘dead’, even though the engine is suffering a bonafide misfire problem.
This is when a manual cylinder balance test saves the day and gets you closer to solving the misfire problem.
You can find this tutorial in Spanish here: Cómo Hacer Una Prueba De Balance De Cilindros (Honda Civic 1.7L) (at: autotecnico-online.com).
Cylinder Balance Test
In a cylinder balance test, one cylinder is ‘shorted’ at a time, while the engine is running.
The purpose of ‘shorting’ the cylinder, while the engine is running, is to see if it affects (worsens) the engine's idle (or not).
Normally, the fuel injectors are disconnected one at a time (to ‘short’ the cylinder). In the 2001-2005 1.7L equipped Honda Civic's, this is pretty hard to do. So, the next best thing is to disconnect one ignition coil at a time.
NOTE: There's one drawback to doing the cylinder balance test by unplugging one ignition coil at a time, and this is that the catalytic converter can get overloaded with raw fuel (it's already overloaded if the engine is misfiring). So, while doing this test, don't leave the ignition coil disconnected too long.
Here's what you'll need to do:
Start the engine and let it idle.
NOTE: This test is done with the engine running. Be careful, stay alert, and think safety all of the time.
Disconnect one ignition coil at a time.
- What you're looking out for is the ignition coil that DOES NOT make the engine's idle worse (when you unplug it from its connector). If this happens, then this cylinder is the ‘dead’ one.
- In a good cylinder (one that's contributing to engine power), when you unplug the ignition coil from its connector, the engine's idle will get worse (it'll be very noticeable!).
Write down your test results.
Let's take a look at what your cylinder balance test results mean:
CASE 1: Unplugging an ignition coil had NO EFFECT on the engine's idle. This test result confirms that that cylinder (this ignition coil belongs to) is ‘dead’ and causing a misfire.
Now that you have found the ‘dead’ cylinder, that's causing the misfire, your next steps are to see what‘s causing the problem.
This means that you need to check that the cylinder has spark, fuel and good compression.
CASE 2: Unplugging any of the ignition coils (one at a time) had NO EFFECT on the engine's idle. This tells you that the misfire is affecting all 4 cylinders and more importantly, it tells you that all of the ignition coils and fuel injectors are working as they should.
Since you have a rough idle condition that can not be pinpointed to just one or two cylinders, I suggest you check:
- Test engine compression. Check to see if compression between cylinders varies more than 15%.
- Vacuum leak from leaking intake manifold gaskets or vacuum hoses.
- Failing fuel pump that is not sending enough volume to the fuel injectors.
Although testing the above conditions is beyond the scope of this article, you now know in what direction you need to take your troubleshooting.
You Found The ‘Dead’ Cylinder. What Next?
Finding out which cylinder, in your 1.7L Honda Civic is misfiring (‘dead’), is half the battle in diagnosing the exact cause of the problem.
My recommendation to you, based on my experience, is to check 3 specific areas:
- Check that the ignition coil, that belongs to the ‘dead’ cylinder, is sparking.
- Check the compression of the ‘dead’ cylinder and make sure it's OK.
- Check that the fuel injector of the ‘dead’ cylinder is OK.
The problem will reside in one of the engine components above (that has failed). You can find the recommended tests explained step-by-step in the following tutorials:
- How To Test The Ignition Coils (2001-2005 1.7L Honda).
- How To Test The Engine Compression (1.7L Honda Civic).
- How To Test The Fuel Injectors (2001-2005 1.7L Honda Civic).
The following tutorial may also come in handy:
If this info saved the day, buy me a beer!