Engine has a misfire

Hi,

First, make sure the spark plug wires are not arcing and are on the correct cylinders. Also, if it is one specific cylinder, pull the spark plug and make sure wasn't damaged, covered with dirt, or the gap closed when installing it.

Here are the directions for testing the ignition system. The attached pics correlate with the directions.

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2005 Chevy Truck Equinox AWD V6-3.4L VIN F
Electronic Ignition (EI) System Diagnosis
Vehicle Powertrain Management Ignition System Testing and Inspection Component Tests and General Diagnostics Electronic Ignition (EI) System Diagnosis
ELECTRONIC IGNITION (EI) SYSTEM DIAGNOSIS
ELECTRONIC IGNITION (EI) SYSTEM DIAGNOSIS

CIRCUIT DESCRIPTION
There are 3 dual-tower ignition coils that are part of the ignition control module (ICM). The ICM contains coil driver circuits that command the coils to operate. The ICM has the following circuits:
- An ignition voltage circuit
- A ground
- An IC 1 control circuit for the 1-4 ignition coil
- An IC 2 control circuit for the 2-5 ignition coil
- An IC 3 control circuit for the 3-6 ignition coil
- A low reference circuit

The powertrain control module (PCM) controls each dual-tower ignition coil by transmitting timing pulses on the IC control circuit to the ICM for the proper coil to enable a spark event.

TEST

Steps 1-8

see pic 1


Steps 9-22

see pic 2

Step 23

see pic 3

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Let me know if that helps. Also, let me know which cylinders are causing the misfire.

Take care and God Bless,

Joe

After checking the spark plugs, I didn’t find anything wrong. so I put a new coil pack in and I’m still registering a misfire. Will perform testing per the literature you sent me and let you know what I figure out.

Hi,

Is the misfire always the same cylinder or cylinders?

Let me know.

Joe

I don’t know. My scanner only says misfire detected.

Is there a code? For example, P0301, p0302, and so on?

Joe

I see where you’re going with this. I didn’t realize that would tell me which cylinder. Yes, but I don’t know off the top of my head which code it’s registering. I’ll have to check that when I get home from work.

P0300.

Hi,

A P0300 is a random/multi-cylinder misfire. Basically, two or more of the cylinders have an issue. A P0300 doesn't indicate a specific cylinder. Since that is the only code, it doesn't seem to be a specific cylinder.

So, here is where I would recommend starting. First, check to see if there are any engine vacuum leaks. That can create a lean fuel mixture and a random misfire. Here is a link to help:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

If you find there are no leaks, next check fuel pressure. A weak fuel pump can cause a lean mixture and a faulty fuel pressure regulator can cause a rich mixture, both of which can cause this. Here is a link that will help:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Here are the manufacturer's specs for fuel pressure:

2005 Chevy Truck Equinox FWD V6-3.4L VIN F
Pressure, Vacuum and Temperature
Vehicle Powertrain Management Fuel Delivery and Air Induction Fuel Pump Fuel Pressure Specifications Pressure, Vacuum and Temperature
PRESSURE, VACUUM AND TEMPERATURE
Fuel Pressure (Key ON, Engine OFF) .................... 384-425 kPa (50-60 psi)

If your scan tool has live data, do this. Plug it in, start the engine, and watch the short-term fuel trims (STFT). If you are able to do this, I will be able to tell if it is a fuel/vacuum-related issue. It will just make it a faster check.

Let me know what you find or if you have other questions.

Take care,

Joe

It was a vacuum leak... thank you for your help.

Hi,

You are very welcome. I'm glad you found it. They can be tricky sometimes. Regardless, I'm glad it's running properly.

Please free to stop back anytime in the future if you have questions. You're always welcome here.

Take care,
Joe