TEST 1: Testing For Spark At The Spark Plug Wire
Whether you know which cylinder is the one that is misfiring or not, I recommend that you test all four cylinders for spark. As mentioned before, the successful outcome of your trouble-shooting/diagnostic lies in the usage of a spark tester.
The following test steps assume that you're gonna' start by testing from the #1 cylinder:
- 1
Remove the spark plug wire (high tension cable) from the spark plug.
- 2
Attach the a spark tester to high tension wire.
Don't have an HEI spark tester? Need to buy one? You can buy it here: OTC 6589 Electronic Ignition Spark Tester. - 3
Connect the spark tester to the battery negative (-) terminal with a battery jump start cable as shown in the photo above.
- 4
Have your helper crank the vehicle as you stand at a safe distance from the engine.
The vehicle may or may start, either way be careful. - 5
As the vehicle cranks or starts, observe the spark tester.
- 6
You're gonna' get one of two results: spark or NO spark.
- 7
Now repeat this test on the other cylinders.
IMPORTANT: Read the following options carefully to interpret your NO SPARK result or results. Remember that some cylinders get spark from the same ignition coil within the coil pack (since the coil pack is made up of two individual ignition coils that have two towers each). So if you get a NO SPARK result from two spark plug wires, you need to verify if they're from paired cylinders 1 and 4 or paired cylinders 2 and 3 or from unpaired cylinders (example of unpaired cylinders would be: cylinders 1 and 3, or 2 and 4, or 1 and 2).
CASE 1: You got spark from all four spark plug wires. This indicates that the ignition coils and spark plug wires are OK. The cause of your misfire condition is not due to a bad ignition coil. Go to: TEST 7: Other Things That Can Cause A Misfire to see further tips and suggestions.
CASE 2: You got NO spark from only one spark plug wire. The next step is to check for spark directly on the coil pack tower that feeds that spark plug wire with spark. Go to: TEST 2: Testing For Spark At The Ignition Coil Pack.
CASE 3: You got NO spark from two spark plug wires that connect to spark plugs for paired cylinders 1 and 4 or paired cylinders 2 and 3. The next step is check for spark directly on both towers (one at a time of course).
For this test go to: TEST 3: Testing For Spark At The Ignition Coil Pack.
CASE 4: You got NO spark from two spark plug wires that DO NOT connect to paired cylinders. The next step is to test each coil pack tower directly for spark one at a time.
For this test go to: TEST 2: Testing For Spark At The Ignition Coil Pack.
CASE 5: You got NO spark from none of the spark plug wires. This usually indicates that power is missing from the power circuit or that the crankshaft position sensor is bad.
To find out, go to: TEST 4: Testing The Power (12 Volts) Circuit.
TEST 2: Testing For Spark At The Ignition Coil Pack
In this test section, you're gonna' test for spark directly on the ignition coil pack tower of the spark plug wire that did not spark in TEST 1.
The best and safest way to accomplish this is by Grounding the spark tester with a battery jump start cable to the battery's negative (-) terminal.
Let's get started:
- 1
Remove the spark plug wire that did not fire off spark from the ignition coil pack.
- 2
Place the spark tester directly on the ignition coil tower of the spark plug wire you just removed (see photo above).
- 3
Connect the spark tester to the battery negative (-) terminal with a battery jump start cable.
- 4
Have your helper crank the engine. The engine may start, so be careful.
- 5
You're gonna' get one of two results: spark or NO spark.
Let's take a look at what your test result means:
CASE 1: You got spark. This spark test result lets you know that the ignition coil is good and that the spark plug wire is defective. Replace all of the spark plug wires (high tension wires) as a set.
CASE 2: You got NO spark. The ignition coil is bad. Replacing the ignition coil will solve the misfire condition and the misfire code lighting up the check engine light (CEL) on the instrument cluster.
