Why does my engine misfire?

Tiny
ELKMAN14
  • MEMBER
  • 2014 FORD F-150
  • 5.0L
  • V8
  • 4WD
  • AUTOMATIC
  • 137,000 MILES
Engine light went on, had checked and was told cylinder four misfire. Changed plugs and coils, engine light went off for day. Went back on next day. Disconnected battery and checked all wires and had test done, number four misfire again. Went off for day, then back on. Had code reset. Went day with it off and then next day back on. Checked plug, no burning or fouling, changed coil with old coil. Added four cans of b-12 chemtool thinking maybe injector. Went hunting next day driving 400 miles round trip, start and stop a lot. Used 4wd a lot. Engine light never came back on that day. Next morning started and light on again. I have had no power loss, very minimal missing, usually only when started and idling in morning. Runs good up hill and towing a pop up camper. No power or speed loss. My truck listed above is the XL model. Thanks
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Thursday, November 8th, 2018 AT 11:09 AM

40 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
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
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Thursday, November 8th, 2018 AT 12:57 PM
Tiny
TRENAROSS
  • MEMBER
  • 3 POSTS
  • 2013 FORD F-150
  • 5.0L
  • V8
  • 4WD
  • AUTOMATIC
  • 129,000 MILES
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.
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Monday, May 10th, 2021 AT 10:44 AM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 107,922 POSTS
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
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Monday, May 10th, 2021 AT 10:44 AM (Merged)
Tiny
TRENAROSS
  • MEMBER
  • 3 POSTS
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
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Monday, May 10th, 2021 AT 10:44 AM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 107,922 POSTS
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
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Monday, May 10th, 2021 AT 10:44 AM (Merged)
Tiny
TRENAROSS
  • MEMBER
  • 3 POSTS
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
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Monday, May 10th, 2021 AT 10:44 AM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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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
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Monday, May 10th, 2021 AT 10:44 AM (Merged)
Tiny
ISGABE
  • MEMBER
  • 1 POST
  • 2010 FORD F-150
  • V8
  • FWD
  • AUTOMATIC
  • 176,000 MILES
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.
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Monday, May 10th, 2021 AT 10:44 AM (Merged)
Tiny
HMAC300
  • MECHANIC
  • 48,606 POSTS
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.
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Monday, May 10th, 2021 AT 10:45 AM (Merged)
Tiny
BIGRAU75
  • MEMBER
  • 3 POSTS
  • 2006 FORD F-150
  • V8
  • 4WD
  • AUTOMATIC
  • 80,000 MILES
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.
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Monday, May 10th, 2021 AT 10:45 AM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 107,922 POSTS
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
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Monday, May 10th, 2021 AT 10:45 AM (Merged)
Tiny
BIGRAU75
  • MEMBER
  • 3 POSTS
I have had a tune up performed on it which seem to fix it thank you.
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Monday, May 10th, 2021 AT 10:45 AM (Merged)
Tiny
BIGBLUEFORD69!
  • MEMBER
  • 2 POSTS
  • 2006 FORD F-150
  • 4.6L
  • V8
  • 4WD
  • AUTOMATIC
  • 193,000 MILES
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.
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Monday, May 10th, 2021 AT 10:46 AM (Merged)
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,468 POSTS
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.

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Monday, May 10th, 2021 AT 10:46 AM (Merged)
Tiny
BMDOUBLE
  • MECHANIC
  • 1,139 POSTS
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.
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Monday, May 10th, 2021 AT 10:46 AM (Merged)
Tiny
2CP-ARCHIVES
  • MEMBER
  • 4,544 POSTS
  • 2006 FORD F-150
  • 173,000 MILES
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.
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Monday, May 10th, 2021 AT 10:46 AM (Merged)
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,468 POSTS
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.
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Monday, May 10th, 2021 AT 10:46 AM (Merged)
Tiny
BM0999
  • MEMBER
  • 1 POST
  • 2005 FORD F-150
  • V8
  • 4WD
  • AUTOMATIC
  • 66,000 MILES
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?
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Monday, May 10th, 2021 AT 10:47 AM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
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.
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Monday, May 10th, 2021 AT 10:47 AM (Merged)
Tiny
ESFX4
  • MEMBER
  • 1 POST
  • 2004 FORD F-150
  • 5.4L
  • V8
  • 4WD
  • AUTOMATIC
  • 176,000 MILES
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!
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