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

Super low compression; truck rocks at certain speeds/RPM and check engine light is intermittently flashing. Spark plug appears to have slight oil residue present even after being changed recently. Strangely no no tics or knocks. Oddly quiet and seems to have better fuel efficiency.

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

Hi Joe,

The fella that tested it said it was at 30 PSI. I have not done the wet test and will try that next. I was thinking it might be a valve problem since there is a small amount of oil on the spark plug and they were just changed on Monday.

Thanks so much for your help; much appreciated!

Trena

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 Joe,

We did both the dry and wet test today. Cylinder 5 isn't reading at all now for either. Thoughts?

Thank you again.
Trena

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

I put the truck on the machine, but it gives no code or no check engine light came on. The truck seems to misfire at forty five mph and fifty five mph. I have taken it to different places and no one can give me the answer.

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.

When I am pulling a trailer and it puts a load on the motor going up hill it starts to miss at higher RPM's. Then when I let off the throttle it quits missing. But now it has started missing at lower RPM's and the miss is getting more noticable even with not much throttle applied. When the miss is occuring the engine light comes on and I have taken it to the dealership and had the computer on it and they can not find a code for anything going wrong can yall give me any ideas about whats goin on.

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

I have had a tune up performed on it which seem to fix it thank you.

I’ve replaced fuel injectors, spark plugs, camshaft and crankshaft sensors. i have switched the coil packs around. I’ve done a vacuum test and my truck is still showing a misfire on cylinder one.

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 a 2006 ford f150 5.4 l triton motor I have had a misfire for months I finally decided to change all the spark plugs at 110000 miles , I had a mechanic put ford motor craft plugs in it and it drove fine for 60000 miles then started to have same problem so I took it to ford and they put it on the lap top and it said I had cylinder 1-2-5 are missing so I changed the spark plug and coils on all 3 , 4 days later it missed again so I took it back to ford the mechanic hooked up the lap top and took it for a ride and said number 5 was missing , I told him I just changed it 4 days ago so he did compression checks and fuel injector checks and they came back all ok. The mechanic says he might think it could be a alternator going bad , now how can I believe him on a quess , so I'm trying to make an appointment to put it on the big computer and do a full truck diagnosis to see what happens , oh not to mention the check engine light never comes on. So I guess my guestion is what else can cause this misfire to happen when the compression and injectors are all ok , and all the injectors were changed at the same time as the plugs and coils.

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.

My 2005 Ford F150 just started to misfire and idle roughly. It is hard to start and there is white smoke from exhaust. I have added fuel injector cleaner, no help. It is the Triton engine. Thoughts?

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.

All cylinders misfiring on driver side. 8,7,6,5 I think those are the right cylinder numbers. Driver side for sure. This happened all at once, and started when I was in park. Check engine light then came on then was flashing. Used a code reader from my brother a couple days after letting it sit after having the issue. And it read this issue as well as VCT solenoid not reading. About eight months ago paid to get the timing chain kit replaced with new E3's and accel boots. Without the plastic tension-er's! After finding plastic guild at the bottom of oil pan. So this year I am on my second spark plug change. My first one years ago was a pain thanks Ford giving me a rebate years after my OEM plugs needed changed. So this Triton engine is on my last dollar I have been more then patiently fixing FORD.LLC stuff on my dollar so they can then learn from our problems. Put a reliable truck together test it then market it!

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

Vehicle sometimes jerks a bit intermittently, engine light came on briefly. pulled over checked oil, then went back home. Ran fine home, but still jerking. Need to make a long trip and worried. I'm thinking fuel filter? Any opinion? Where is the filter located?

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-

The pickup was throwing a P0301 OBD code and I decided to change the ignition coil. That seemed to have fixed the problem for a little bit, but it threw the same code again for the same cylinder. Could this mean that it is something more serious?

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

Hi Joe,

So I ended up changing the spark plug since I didn't replace it when i was changing out the coil. The code did go away for around two days but then it came back. The misfire doesn't change to a new cylinder, the scanner keeps saying that it is cylinder one.

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

changed spark plugs on all 6 cylinders, changed 02 sensors truck still missing

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.

I got all new fuel injectors that fixed it thank you.

I am at my whits end! I bought the truck listed above about 8 months ago. I was told the truck had the 5.4l originally but had to be replaced about 2 years ago and now has the 4.6l. I was told that it had a miss but that it was not all the time and all I had to do was throw it in neutral and rev it up and it would clear up.for 8 months now I have had a yard ornament! I have replaced all plugs and cool packs and it continuously throws a multiple misfire code everyday for a different cylinder! I can't keep replacing these things just to start it up get to the end of my driveway and have to turn around. please, please help me! This is my only transportation and I am going crazy!

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

Okay, I will have those checked. Thanks so much!

I changed out number four coil pack, changed all the spark plugs and cleared the code. It continued to miss fire and the light came back on, I took number three and number four coil packs and switched them out, cleared the code and still getting a miss fire on number four cylinder. I notice that number four fuel injector had a little corrosion. So I replaced the injector and the wire connectors still getting a miss fire. I am now thinking the plug and the coil pack may not be getting any fire. How do I check it and . What is your opinion, I am baffled.

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.

XLT model 5.4L V8. Recurring cylinder four misfire after eight new coils, eight new spark plugs, one new fuel injector on number four, compression test passed. Any ideas?

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

Thanks you so much. I figured out using the guide and the wiring diagrams I had a broken wire to the coil. A simple fix!

Driving when suddenly I felt a shudder as if transmission was lagging then I accelerate and truck sounds like I am running on one cylinder with a deep clicking sound, almost like a vacuum loss or dead cylinder. No problem with truck up to that point. Service engine light is on now but after its on for a bit it flashes quickly then goes back to still position then flashes again.

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.