Power Transistor Test And Ignition Coil Test 2.4L Nissan Altima (1993-1997)

TEST 1: Testing For Spark At The Spark Plug Wires

The most logical starting point, whether your Nissan Altima is suffering a no-start or a misfire condition, is to test for spark at the spark plug wires.

Now, you might already have a specific cylinder you want to test first (if you have a specific misfire diagnostic trouble code: P0301, P0302, P0303, P0304) or you may not know what specific cylinder is the one misfiring or your Altima just doesn't start. Well, my recommendation is to test all of the spark plug wires for spark regardless.

I want to stress the importance of using an HEI spark tester to perform all of the spark tests (don't have an HEI spark tester? Need to buy one? You can buy it here: OTC 6589 Electronic Ignition Spark Tester). Here are a couple of other important suggestions:

1. Do not use a regular spark plug in place of a spark tester.
2. Do not pull the spark plug wire off of its spark plug while your helper cranks the engine to verify spark. This will damage the ignition coil, if it isn't fried already.

OK, here we go:

1. 1

   Disconnect the spark plug wire from its spark plug.

2. 2

   Attach the HEI spark tester to the spark plug wire.

3. 3

   With a battery jump start cable, attach the HEI spark tester to a good Ground point or to the battery negative (-) terminal.

4. 4

   Have your assistant crank the engine while you eye-ball the spark tester. If you're testing a misfire condition, the engine will start, so be careful.

5. 5

   Repeat the test for all of the remaining spark plug wires (if applicable).

6. 6

   You're going to see only one of two results: either spark jumping across the HEI spark tester's air gap or no spark.

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

CASE 1: You got spark on all of the spark plug wires. This results let's you know that the power transistor, ignition coil, distributor rotor and cap are OK. You do not have to perform any of the other tests in this article.

Having all of the spark plug wires firing off spark eliminates all of these components as the cause of your misfire codes or 'no-spark no-start' condition. Since your Nissan Altima is still misfiring, go to: Other Causes Of A Misfire and check out the suggestions presented in that test step.

CASE 2: You got NO spark from any (none) of the spark plug wires. The next step is check that the ignition coil is creating and feeding spark to the distributor cap. You'll accomplish in TEST 3. Go to: TEST 3: Testing The Ignition Coil's High Tension Wire.

CASE 3: You got spark on some but not all of the spark plug wires. The next step is check for spark directly on the distributor cap towers that feed spark to these wires that did not fire off spark. Go to: TEST 2: Testing For Spark At The Distributor Cap.

TEST 2: Testing For Spark At The Distributor Cap

A very common problem that can a misfire condition on your Nissan Altima, is when one or more of the distributor cap's towers don't transmit the spark to their respective spark plug wires.

Fortunately, this can be verified very easily by testing for spark directly on the distributor's cap tower whose spark plug wire did not spark in TEST 1.

Important: this test is only for when one or several (but not all) of the spark plug wires did not spark!

1. 1

   Remove the spark plug wire (that didn't spark) from its tower on the distributor cap.

2. 2

   Place the spark tester directly on the tower as shown on the photo above.

3. 3

   Ground the spark tester to the battery negative (-) terminal with a jump start cable.

4. 4

   Have your helper to crank the engine while you observe the HEI spark tester.

5. 5

   Repeat this test with the others that did not fire off spark (if applicable).

You'll see one of two results: the HEI spark tester sparking or no spark. Let's analyze each of these results below:

CASE 1: You got spark. This test result indicates that the spark plug wire is bad, replace all of them as a set. This will solve your misfire condition and misfire codes lighting up your check engine light (CEL) on your Nissan Altima. Now, if the rest of the distributor components (distributor cap and rotor) are as old as the spark plug wires you're replacing, I recommend replacing them too.

Here's the why of the no spark result: As the spark plug wire gets older, its normal resistance to spark increases to the point that the it can't and doesn't channel spark to the spark plug. This will either cause a misfire, or a lack of power, or a no-start condition. Spark plug wires don't last forever, especially after-market ones (average life-span is 3 to 4 years).

CASE 2: You got NO spark. This result lets you know that the distributor cap is bad. Replace the distributor cap and distributor rotor as a set. This should solve your misfire problem. Now, if the rest of the distributor components (spark plug wires and spark plugs) are as old as the distributor cap and rotor you're replacing, I recommend replacing them too.

Here's why: As the distributor cap ages, the terminals that transmit the spark to the spark plug wires corrode. This corrosion increases the resistance to spark and over time (as more corrosion is created) this same corrosion stops the spark from passing thru' to the spark plug wires.

TEST 3: Testing The Ignition Coil's High Tension Wire

The ignition coil's high tension wire, that transmits the spark to the distributor cap, can go bad.

The good news is that this high tension wire can be easily tested and that's what we're gonna' start doing with this test step.

This is what you'll do:

1. 1

   Disconnect the end of the ignition coil's high tension wire that connects to the distributor cap.

2. 2

   The other end of the high tension wire must remain connected to the ignition coil.

3. 3

   Connect the HEI spark tester to the end that you just disconnected.
   
   This can be a bit tricky since the HEI spark tester will not connect securely to the terminal of the high tension wire. If the HEI spark tester comes loose when you crank the engine, you can use a small piece of black electrical tape to hold it in place.

4. 4

   Ground the HEI spark tester with the battery jump start cable to the battery negative (-) terminal.

5. 5

   Have your helper crank the engine as you hold the HEI spark tester in place.

6. 6

   You'll get one of the 2 results: (1) spark or (2) no spark.

Let's analyze each result in more detail below:

CASE 1: The spark tester sparked. This result confirms that the distributor cap is bad. Replace the distributor cap and rotor as a set and your no-start condition on your Nissan Altima should be solved. If the spark plug wires are as old as the distributor cap you're replacing, I suggest you replace them too along with the spark plugs.

CASE 2: The spark tester DID NOT spark. The next step is to test for spark directly on the ignition coil's tower. Go to: TEST 4: Testing The Ignition Coil For Spark.