Why does my engine misfire?

The fact that one side is having a problem I would lean toward the timing chain having a problem. Let's do a compression test to confirm the failure.

https://www.2carpros.com/articles/how-to-test-engine-compression

and

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

Please let us know what you find. We are interested to see what it is.

Cheers, Ken

Hello, I'm Danny.

Well, first things first. you need to have the check engine light codes to be retrieved.If you don't have access to a code reader/scanner most auto parts store like AutoZone will check for free.Here is a tutorial showing what is involved retrieving check engine light codes:

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

After you have the codes checked please get back to us with the information to help us properly diagnose the truck.As far as fuel filter it's located on the left side of the frame rail inside about mid point. I've attached a picture.I would suggest getting the code(s) first before replacing fuel filter.Hope this helps and thanks for using 2CarPros.
Danny-

Welcome to 2CarPros.

Anything is possible. However, did you replace the spark plug at the same time? If you move the coil pack to a different cylinder and clear the code, do you still have a number one misfire or does the misfire change to the new cylinder?

https://www.2carpros.com/articles/how-to-tune-up-a-car-engine

Let me know

Joe

Welcome back:

Okay, since we know the plug and coil are both not the cause, we have to consider the following.

Compression issue
Fuel injector issue
Timing issue

At the present mileage, I would confirm that compression isn't low in that cylinder. As far as the timing, if it is playing a role, you will see it in the compression reading. Here is a link that explains in general how to check compression:

https://www.2carpros.com/articles/how-to-test-engine-compression

https://www.2carpros.com/articles/symptoms-of-low-compression

Here are the specifics for your vehicle when checking compression. The two attached pictures relate to your findings.

_____________________________

Compression Test-Compression Gauge Check
1. Make sure the oil in the crankcase is of the correct viscosity and at the correct level and that the battery is correctly charged. Operate the vehicle until the engine is at normal operating temperature. Turn the ignition switch to the OFF position, then remove all the spark plugs.
2. Set the throttle plates in the wide-open position.
3. Install a compression gauge such as the Compression Tester in the No. 1 cylinder.
4. Install an auxiliary starter switch in the starting circuit. With the ignition switch in the OFF position, and using the auxiliary starter switch, crank the engine a minimum of five compression strokes and record the highest reading. Note the approximate number of compression strokes required to obtain the highest reading.
5. Repeat the test on each cylinder, cranking the engine approximately the same number of compression strokes.

Compression Test-Test Results
The indicated compression pressures are considered within specification if the lowest reading cylinder is at least 75 percent of the highest reading. Refer to the Compression Pressure Limit Chart.

Part 1 Of 2
pic 1

Part 2 Of 2
pic 2

Compression Pressure Limit Chart
If one or more cylinders reads low, squirt approximately one tablespoon of engine oil on top of the pistons in the low-reading cylinders. Repeat the compression pressure check on these cylinders.

Compression Test-Interpreting Compression Readings
1. If compression improves considerably, piston rings are faulty.
2. If compression does not improve, valves are sticking or seating incorrectly.
3. If two adjacent cylinders indicate low compression pressures and squirting oil on each piston does not increase compression, the head gasket may be leaking between cylinders. Engine oil or coolant in cylinders could result from this condition.

Use the Compression Pressure Limit Chart when checking cylinder compression so that the lowest reading is within 75 percent of the highest reading.

___________________________________

I realize this is a lot of work to do, but since it keeps coming back to the same cylinder, we need to start somewhere to diagnose the cause.

Please feel free to let me know if you have other questions or need help.

Take care,
Joe

There's a number of other things to consider for a single-cylinder misfire. First try swapping two injectors to see if the misfire moves to a different cylinder. I would do a full tune up with coils this guide should help and check out the video below it.

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

and

https://youtu.be/e68QXyBAiZo

Please run down these guides and report back.

Good morning,

Two things I would check right off the bat.

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

1. Fuel pressure. misfire codes can be set from low fuel pressure from a bad fuel pump.

2. Compression test. Test all cylinders to be sure there is no internal damage to any of the cylinders.

https://www.2carpros.com/articles/how-to-test-engine-compression

Roy

I have seen this problem before which I had to replace the PCM because the injector driver was weak and couldn't open the to let the fuel in here iws how you replace the PCM in the diagrams below.

This guide can help as well

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

Check out the diagrams (Below). Please let us know what happens.

I would see if the injector and the ignition coil is getting pulse you could have a connection problem between the injector/coil and the PCM. Here is a guide to help you test the connections and confirm the injector coil operation:

https://www.2carpros.com/articles/how-to-test-a-fuel-injector

and

https://www.2carpros.com/articles/how-to-test-an-ignition-system

and

https://www.2carpros.com/articles/how-to-check-wiring

Here is the engine wiring diagrams so you can get started. Check out the diagrams (below). Please let us know what happens.

Cheers

You will have to scan it for codes to see if anything like a sensor has gone out.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

I would do a full tune up with coils this guide should help and check out the video below it.

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

and

https://youtu.be/e68QXyBAiZo

Please run down these guides and report back.