Why does my engine misfire?

Good afternoon.

It does sound like an injector that may have an irregular spray pattern causing the misfire but to be sure this guide can help us

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

and the video

https://youtu.be/e68QXyBAiZo

I would try moving the injector to another cylinder and see if the misfire travels with it. That will confirm it is an injector.

Roy

Possibilities below

P0304
Descriptor
Cylinder 4 Misfire Detected
Probable Causes
Engine Mechanical Malfunction
Evaporative Emissions (EVAP) System Malfunction
Evaporative Emissions (EVAP) System Purge Valve
Exhaust Gas Recirculation (EGR) System
Fuel Injector 4
Fuel Pressure Incorrect
Ignition System Malfunction
Misfire Monitor Neutral Profile Correction Has Not Been Relearned Since Last Repair
Vehicle Running Out of Fuel

Hi,

As far as the misfire, it is likely being caused by low compression. Can you tell me the compression readings you got when it was checked? Also, was a wet compression test performed to see what could be the cause of the low compression in one cylinder?

A wet test is when you put a small amount of engine oil into the cylinder and retest the compression. If the compression is higher then you know it's a piston ring problem because the oil will temporarily seal the rings to the cylinder wall.

Here is a link that explains this in better detail. You will have to page down a bit to locate the directions for this procedure.

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

Here is a link that discusses reasons for low compression:

https://www.2carpros.com/articles/the-reasons-for-low-compression

Let me know. Also, let me know if you ever notice a back fire or anything other you can think of that may help me diagnose the issue.

Take care,
Joe

Trena,

If it is at 30, we have bigger issues than a vacuum related issue. If you follow the link I provided above, check the compression both dry and wet so we can confirm what you were told. For it to be that low, something has happened internally.

Let me know what you find.

Joe

Hi,

If there is no compression, it sounds like either we have a bent or stuck valve (open) or a hole in the piston.

I would start by removing that side valve cover and see if the valves for that cylinder are moving.

Here are the directions for removing the left side valve cover (cylinder 5). The attached pics correlate with the directions.

______________________________________________

2013 Ford Truck F 150 4WD V8-5.0L
Valve Cover - LH
Vehicle Engine, Cooling and Exhaust Engine Cylinder Head Assembly Valve Cover Service and Repair Removal and Replacement Valve Cover - LH
VALVE COVER - LH
Valve Cover
- LH

See pic 1 to 4

Removal

NOTICE: During engine repair procedures, cleanliness is extremely important. Any foreign material, including any material created while cleaning gasket surfaces, that enters the oil passages, coolant passages or the oil pan, can cause engine failure.

1. Remove the Air Cleaner (ACL) outlet pipe and the ACL (Air Cleaner) cover as an assembly.

2. Remove the crankcase ventilation tube. For additional information, refer to the quick connect coupling procedure in Fuel Delivery and Air Induction.

Pic 5

3. Remove the LH ignition coils. For additional information, refer to Ignition System.

4. Disconnect the 2 LH Variable Camshaft Timing (VCT) variable force solenoid electrical connectors.
- Detach the 10 wiring harness retainers.

Pic 6

5. Remove the oil level indicator.

6. NOTICE: Do not use metal scrapers, wire brushes, power abrasive discs or other abrasive means to clean the sealing surfaces. These tools cause scratches and gouges which make leak paths. Use a plastic scraping tool to remove all traces of old sealant.
Loosen the 14 bolts and remove the LH valve cover and gasket.
- Clean the valve cover mating surface of the cylinder head with silicone gasket remover and metal surface prep. Follow the directions on the packaging.

- Discard the valve cover gasket. Clean the valve cover gasket groove with soap and water or a suitable solvent.

7. Depress the 4 tabs and remove the oil level indicator tube.

Pic 7

8. Inspect the 2 VCT (Variable Camshaft Timing) variable force solenoid seals. Remove any damaged seals.
- Using the Differential Bearing Cone Installer and Handle, remove the seal(s).

Pic 8

9. Inspect the spark plug tube seals. Remove any damaged seals.
- Using the VCT (Variable Camshaft Timing) Spark Plug Tube Seal Remover and Handle, remove the seal(s).

Pic 9

Installation

1. NOTE: Installation of new seals is only required if damaged seals were removed.
Using the VCT (Variable Camshaft Timing) Spark Plug Tube Seal Installer and Handle, install new spark plug tube seals.

Pic 10

2. NOTE: Installation of new seals is only required if damaged seals were removed.
Using the Differential Bearing Cone Installer and Handle, install new VCT (Variable Camshaft Timing) variable force solenoid seal(s).

Pic 11

3. NOTE: If the valve cover is not installed and the fasteners tightened within 5 minutes, the sealant must be removed and the sealing area cleaned. To clean the sealing area, use silicone gasket remover and metal surface prep. Failure to follow this procedure can cause future oil leakage.
Apply an 8 mm (0.31 in) bead of silicone gasket and sealant to the engine front cover-to-LH cylinder head joints.

Pic 12

4. Position the LH valve cover and new gasket on the cylinder head.
- Tighten the bolts in the sequence shown to 10 Nm (89 lb-in).

Pic 13

5. Install the oil level indicator tube.
- Push the oil level indicator tube into the valve cover until it clicks into place.

6. Install the oil level indicator.

7. Connect the 2 LH VCT (Variable Camshaft Timing) variable force solenoid electrical connectors.
- Attach the 10 wiring harness retainers.

Pic 14

8. Install the LH ignition coils. For additional information, refer to Ignition System.

9. Install the crankcase ventilation tube. For additional information, refer to the quick connect coupling procedure in Fuel Delivery and Air Induction.

Pic 15

10. Install the Air Cleaner (ACL) outlet pipe and ACL (Air Cleaner) cover assembly.

_______________________________

Once it's off, turn the engine to see if the valves are moving.

Let me know what you find.

Joe

It sounds like you might need a tune up or have a bad spark plug-coil (common), injector or low compression to be sure which one it is please follow these videos and guides.

https://youtu.be/QTE8k06MzwQ

and

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

and

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

Let us know what happens and please upload pictures or videos of the problem.

It could be many things. If the light came on, there should be a code stored.

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

Honestly, this type of problem usually is caused by needing a tune up, dirty air filter, or a weak fuel pump. If you need directions on how to check the fuel pump, let me know.

Joe

Hello,

The first thing I would do is check the compression on one and if okay I would replace the MAF sensor with a new Motorcraft unit. Here is a guide to help you with the repair with diagrams below for your car:

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

and

https://www.2carpros.com/articles/how-to-replace-a-mass-air-flow-sensor-maf

Check out the diagrams (below). Please let us know what you find. We are interested to see what it is.

I would start with a relative compression test, press the accelerator pedal all the way down while cranking the engine and listen to how the engine sounds. Should be uniform without and higher pitch rpm flare ups, which indicate a lower compression on one or more cylinders.

I have seen the coils go out in these trucks here is a guide and a video on how to fix it.

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

and

https://youtu.be/e68QXyBAiZo

Please run down these guides and report back.

Engine misfiring can be caused by worn spark plugs, a weak spark (weak coil, bad spark plug wire). 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.