Doing a manual cylinder balance test will 'nail down' the misfiring cylinder (also known as a 'dead' cylinder) that's causing your 1.6L Toyota Corolla (1.6L Geo Prizm) to idle rough.
Why perform a manual cylinder balance test? The short answer is to save time, frustration and money in trying to find and solve the exact cause of your Corolla's (Prizm's) engine rough idle or engine miss. This applies particularly to the non-OBD II Corollas that don't have misfire diagnostics. Even if your Toyota is OBD II equipped, there are times the PCM can't or doesn't pinpoint the misfiring cylinder.
This is when a manual cylinder balance test saves the day and gets you closer to solving the misfire problem.
Contents of this tutorial:
You can find this tutorial in Spanish here: Cómo Hacer Una Prueba Balance De Cilindros (1.6L Toyota Corolla) (at: autotecnico-online.com).
APPLIES TO: This tutorial applies to the following vehicles:
- 1.6L (4A-FE) Toyota Corolla: 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997.
- 1.6L (4A-GE) Toyota Corolla: 1989, 1990, 1991.
- 1.6L Geo Prizm: 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997.
Cylinder Balance Test
The purpose behind the cylinder balance test is to 'short' one cylinder at a time while the engine is running.
If the cylinder you're 'shorting' is 'dead' (misfiring), then 'shorting' won't affect (worsen) the engine's idle. If the cylinder IS NOT 'dead' to begin with, then 'shorting' WILL cause your Corolla's engine's idle to worsen.
What makes doing the cylinder balance test so easy is the fact that the fuel injector electrical connectors are very accessible, since these are the ones we need to disconnect and reconnect (one at a time) to 'short' the cylinder.
Here's what you'll need to do:
- 1
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. - 2
Disconnect the cylinder #1 fuel injector.
- 3
Observe the engine idle. Does the engine idle become rougher?
If the cylinder is 'dead', unplugging the fuel injector WILL NOT make the engine's idle worse.
In a good cylinder (one that's contributing to engine power), when you unplug the fuel injector from its connector, the engine's idle will get worse -it's that noticeable! - 4
Reconnect the fuel injector.
- 5
Observe the engine idle. Does the engine idle improve?
In a good cylinder (one that's contributing to engine power), when you unplug the fuel injector from its connector, the engine's idle will get worse. When you reconnect the fuel injector, the engine idle improves. - 6
Repeat steps 2 thru 5 several times to make sure of your test result.
- 7
Identify the cylinder that's 'dead' using the illustration at the beginning of this tutorial.
- 8
Repeat steps 2 thru 7 on the remaining fuel injectors.
Let's take a look at what your cylinder balance test results mean:
CASE 1: Unplugging an fuel injector had NO EFFECT on the engine's idle. This test result confirms that that cylinder (this fuel injector 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 fuel injectors (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 fuel injectors 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 1.6L Toyota Corolla (1.6L Geo Prizm) is misfiring ('dead'), is half the battle in diagnosing the exact cause of the problem.
The next step is to find out if the misfire is due to a lack of spark, or a lack of fuel, or a lack of compression.
My recommendation to you, based on my experience, is to check 3 specific areas:
- Check the ignition system:
- Check that each spark plug wire is feeding spark to the spark plug with a dedicated spark tester.
- Check that the spark plugs are not worn out, cracked/broken, or swimming in oil from a defective spark plug tube seal.
- Check the fuel injectors:
- Resistance test each fuel injector to see if any one of them is fried internally.
- Check the fuel injector activation signal with Noid light.
- Check the compression of the 'dead' cylinder and make sure it's 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 Engine Compression (1989-1997 1.6L Toyota Corolla).
- How To Test The Fuel Injectors (1993-1997 1.6L Toyota Corolla).
- Troubleshooting A Hard To Diagnose Misfire Case Study (GM 3.1L, 3.4L).
- Carbon Tracks Are A Common Cause Of Ignition Misfires (at: easyautodiagnostics.com).
- Diagnosing A Toyota Corolla Misfire Case Study (1.8L Toyota Corolla).
Where To Buy The Tools You Need
Check out the following links and comparison shop the specific tools you'll need to diagnose the misfire (rough idle) on your 1.6L Toyota Corolla (1.6L Geo Prizm):
The best place to comparison shop and buy is online. I now buy all of my tools online to save.
More 1.6L Toyota Corolla Tutorials
There are several more 'how to' tutorials that I've written that are 1.6L Toyota Corolla specific, that may be of further help. You can find them here:
Here's a small sample of the tutorials you'll find in the index:
- How To Test The Front O2 Heater (1996-1997 1.6L Corolla).
- How To Test The Rear O2 Heater -P0141 (1996-1997 1.6L Corolla).
- How To Retrieve Toyota Corolla OBD I Trouble Codes (1990-1995 1.6L Toyota Corolla).
- How To Test The Throttle Position Sensor (1989-1997 1.6L Toyota Corolla).
If this info saved the day, buy me a beer!
