How to Fix a Engine Misfire Code P0301 (Spark Plugs and Wires)

How to Fix a Engine Misfire Code P0301 (Spark Plugs and Wires)


one, two, three, four! Rev up your engines! It’s time for the Scotty Kilmer Channel if your vehicle has a misfire then stay
tuned, because today I’m going to show you how to fix a vehicle that has a
misfiring engine, now in this case the Ford truck is running poorly, but it also
has a code, and has a code for misfire on cylinder number seven, engine light was
on, so that warned us that there was a code in the computer, now unfortunately
many things can cause a cylinder misfire so we’ll start by finding cylinder
number seven and checking the spark plug, on this Ford v8 the number seven spark
plug is the third one in on the right-hand side, when we reach down here
and pull the spark plug wire off, look stupid wires broken, so this could be the
easiest fix of all time, but we’re going to check the spark plug anyways, to see if
it’s worn out, so we’ll unscrew the spark plug and take a look at it, it is an old
truck, but you see there’s a bunch of carbon that’s burnt on it, so we’re going to
change all the spark plugs too, now let’s face it, since this one spark plug boot was
all cracked and ripped, the others are just as old, so we’ll change
the whole spark plug wire set, now as you can see, I’ve just had a thunderstorm
so filming was interrupted for a little while, but now we’ll go back to fixing
the truck, now changing the spark plugs is easy, you just get a socket put the
new spark plugs in, first you want to twist them in hand tight, so they’re
somewhat snug, then you finish up by making a nice and tight with a ratchet,
turning them till they don’t move any more, just pull up so they’re nice
and tight, if you notice when you buy good new spark plug wires they come with
little package of silicone grease, and you put a little bit of that grease on
the end that plugs into the ignition coil, and also a little bit inside the spark
plug boot, so where it goes on the spark plug the metal gets good contact, and
since there’s not much working room on these trucks and they’re high, I get a little
step and climb up, that way I can push the wires in better, and not hurt myself
squeezing too much, and as I said be sure to do all of the spark plugs and wires,
because if one is worn and cracked the rest are soon to follow,
and if you want to know the trick for getting the back two spark plugs on this
Ford v8, you jack it up and go under the fender well, as
you can see, the spark plug is hiding right in here, you get a long extension and a
spark plug socket and they come right out, just stick the socket on, and you can get the
plugs right out, as you can see this, plug is really worn out, I don’t think
anybody’s ever changed it in the life of this truck, it’s so hard to get to,
now you might end up all hot and sweaty with it being hot and rainy, but at least
you’ll get the job done, and now comes the moment of truth, well it’s humming like a top now, we got it done, and remember if you’ve got any car
questions just visit Scottykilmer.com and I’ll answer him as soon as I get
done with this 1952 Ford!

100 comments

  1. Hey Scotty, I have a 2006 Honda v6 accord . Codes are reading that all valves are misfiring. Changed all the spark plugs, the old ones were carbonized. How long til the emissions light resets and should I do anything else? Spark plug wires?

  2. I have cylinder 3 misfire I change coilpack I changed my fuel inject I changed spark plug and my car compression is still good off by 3 points help running out of ideas

  3. Hi Scotty, sometimes after driving for a little while 20mins or so when i put my foot on the acclerator, the exhaust sounds louder and discontinuous. This sound goes straight away when I restart the engine strangely! could this be due to engine misfire or somethung else?
    But as i said it doesn't always come on and goes away when i restart the engine!
    any ideas or suggestion is much appreciated

  4. Hey scott, where'd you buy that scan tool? I been looking for one but i haven't had any luck and some were very expensive

  5. Hello Scotty i have a 2001 toyota camry V6. this car just stop in the highway and want start again i towed it to home jump it and add fuel now the car can start but engine is verry loud and when i try to press the gas pedal it doesnt work when i keep pressing i have blinking check engine light. i change spark plug and the 3 injectors same problem. please can you help me??

  6. LOVE YOUR VIDS! KEEP THEM COMING. IF MY CAR WOULD MAKE IT TO YOU I WOULD BRING IT TO YOU TO FIX…ITS A MUSTANG AND SHE IS A REAL BITCH. SEMPER FI

  7. I've got a 2006 Silverado that has a misfire. The spark plugs and wires were just replaced. While in harsh driving when there's a lot of wind resistance, my check engine light will flash. A relative who worked for Toyota for over 20 years said he could feel my truck misfiring. How can I find out what it is?

  8. The misfire code on my wife's 2009 Chevy Malibu P0304 turned out to be a burnt exhaust valve. A compression test on cylinder 4 turned this up. The engine only had about 100k miles on it at the time and had never been abused (to my knowledge). Sigh.

  9. Amazing video Scotty, thanks for posting it. I just finished replacing radiator coolant and using the Steel Seal you recommend for engine gasket fixing. After completing the process the engine runs much smoother with high compression. However, scan still shows PO3 cylinder 4 misfires. What should I do? Thanks.

  10. What could cause a car (manual trans) with no cel, to drop rpms but go back up and when it drops rpms it slightly feels like it stalls but doesn't. All while in gear and only happens once in a while

  11. Hello Scott, could you show how to use a snap on 5 gas analyzer to check all your emissions in your engine.
    Thank you.

  12. Hello there,
    I have a 2011 Infiniti G37xs and the car one day drive great and very smooth and the next day you'll notice like you forget your hand break on , if you're driving down the hill and you let go the gas for a little you'll feel like the car wants to stop !! Do you have any idea what's going on? I changed spark plugs and air filters and I cleaned the maf sensors and nothing happened!!
    Thanks Scotty.

  13. thanks my mazda rx8 check engine light turned on this helped alot. i ran the obd2 diagostic tool and i had a misfire in cyl 1

  14. hey scotty you've helped me b4 and I appreciate it! so now I have a 07 sonata and a misfire p0303 so got a new coil for it now it says misfire 6 check engine light is back on..plz help! uggh!!!

  15. got a question scotty when im driving around town all day, no misfire, but after im driving on the freeway for say 30 minutes it misfires, lose power, pull over turn off, start back up its normal again? driving me crazy, no misfire codes either?

  16. hello on a flooded car the spark plugs fires all the time when you turn the ignition on any idea what the problem is . no water in gas or oil or transmission . . fires random and often for no reason. .

  17. Hey people i have a question i just got my spark plugs n wires changed n now there in idled at a red light or just in drive with my foot on my break its starts to like chug n choke n shake a bit any ideas? I dont have a engine lite ether so i dont know whats wrong its never happen it just started after i got them changed

  18. Use a torque wrench when tightening those spark plugs. Most heads are aluminum, these days, and can be stripped easily. Get the proper tightening spec from your Hanes Manual, or similar.

  19. hey Scotty, I replaced my ignition coils and fuel injectors but now my engine has a rough idle, what could it be? it's a 5.3 01 GMC Sierra

  20. Seriously.
    Screw them in by hand and then tighten them with a wrench till you can't turn them anymore?
    People ignore that statement.
    I think some electricity had shorted to his brain from that lead in the water

  21. Hello Guys. I got one useful video on how to find a misfire problem on most of the cars. Hope it will help.
    Thank you
    https://www.youtube.com/watch?v=DL8AILkCyjY

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  23. Hi Scotty, i just checked out a 1996 s10 4 cyl….its only running on 2 cylinders and when i start it up after filling radiator water just shoots out of opened radiator top…know water seems to be in oil…and i am pretty sure i can fix miss if i buy it,but not sure if water shooting out is normal…. if you could let me know what could be cause i would be very happy… not sure if i should buy this truck or not….thanks

  24. My spark plugs hole is stripped out. I rethreaded it once before and the new spark plug blew a second time and now the second rethreaded doesn't hold the plug. Can I just not use the cylinder?? If so what do I do with the open plug hole?

  25. I have a 2008 Mercury Mountaineer V6 4.0L and I am having a random misfire issue on cyl 5 as well as "hard shifting" on 2nd and 3rd gear. I'm not sure if they are the same issue or separate. I have heard that misfires can be misdiagnosed as hard shifting. Neither issue is every time and they don't throw a code every time. Recent maintenance I've done includes water pump, harmonic balancer, belt, plugs, and leads. The misfire was prior to all that, these were all things I found looking into the misfire issue. The misfire seems like it could be the EGR? I am getting both negative and positive readings on my EGR_ERR with my OBDII software, telling me it isn't always moving the amount the computer is calling for. Maybe I'm going down the wrong path… Any ideas? My misfire will go away after shutting down the vehicle and restarting it. Sometimes I have to start/restart the Mountaineer multiple times before it will run fine, other times it will start fine and run but still has a "hard shift" at 2nd and 3rd gear here and there. Any help would be greatly appreciated!

  26. I replaced wires and coil packs and spark plugs but I’m still only running on 2cyl need help if anybody knows anything else I could do

  27. How to tell which is what cylinder? I have a check engine for misfire on cylinder 5 and 8, but i dont know which one is that? Any suggestion? 04 Ford crown Victoria

  28. I wish you were my father. He is a mechanic and has four of us daughters and wont teach us anything about vehicles. He always suggest we go to a mechanic. I learned how to repair & replace almost everything on both my Rovers and Jaguar by myself by reading and doing it on my own. Started back in 2004 Looking it up on google, printing out directions, buying parts, buying all my tools, jacks and taking my time and doing it on my own. Even til this day he refuses to give me advice about the vehicles when im stumped. You are a great teacher and im glad you are making these videos for other determined women like me. Thank you so much. I appreciate you.

  29. What about if you have a misfire on bank 5,6,7,8 could it attain to the SAI (secondary air inlet) or the fact that i removed some spark plugs to check them and noticed some were hand loose.

  30. fixed a misfire with 3$ spark plugs. the engine was misfiring randomly and when you gave it gas it stopped. i thought it would be a fuel injector or something worse and the plug looked healthy, but when i changed them it fixed the problem

  31. Does anyone know why a engine would misfire under a heavy load only ? Wot. The engine runs flawless 90 percent of the time except sometimes at full throttel it will do like a sputter almost like high speed miss from 3500 to 6000 only ?? I'm stumped its a 85 mustang 5.0 with a carb ever thing is dialed in . Lifter

  32. 6 years after posting and your vids are still the best and most engaging. great pace and entertaining to watch. makes car pain more bareable cheers Scotty.

  33. Question if ya don’t mind, I’m currently having a problem with a PO305 , PO300 random misfire , and a small evap leak. I’ve changed the spark plugs , the coil packs are fine and the wires don’t look bad, but the trucks CEL. Flashes if I get above 3500 then for a minute the truck shakes and I have a rough idle. What can else should I do to fix it ?

  34. Thank you so much for these videos. I'm a bad ass single mom who is to learning to fix my car myself if I can before I take it to a mechanic. You have saved me so much money and so many headaches.

  35. I have a 2003 Nissan Altima that is misfiring also losing complete power while driving It will not go over 1000rpm I will pull over turn the car off about five minutes crank it put it in drive it will run for a while then it does the same thing again what’s wrong?

  36. Hi, Scotty I have my mechanic did the stripped spark plug fixed. After he installed everything and Cylinder 5 is still making noise and misfiring do you have any solution for this?

  37. SCOTTY I had a broken plug in the motor all the plugs are new how the heck does that happen misfire code after 4 weeks po303////?///

  38. Can I rely on OBD data to find out the right time to change spark plugs? If I change "old" spark plugs based on the Toyota maintenance sheet, they look like new.

  39. Any body can tell me what i can do to my 97 Toyota 4 runner is miss firing i replace coils wight new boots spark plugs and wires and still shows engine light and missfireing still

  40. Hello everyone, I have Ford Taurus 2007, car runs great and smooth, but consuming more fuel as 3 of its cylinder are misfiring (cylinder 4,5,6 to be exact). I got following codes from OBD scanner : P300, P304, P305, P306 for misfire of those cylinder, I also got P175 for 'System too Rich Bank 2', and P430 for 'Catalyst system efficiency below threshold Bank 2'. I have checked the ignition coil's primary and secondary resistances. Primary resistances were (1.1, 1.1, 0.8 ohms respectively) and secondary resistances were (10.30, 10.24, 10.14 kilo-ohm respe.). So ignition coil seems good, the spard plugs are also replaced recently, spark plug wires seems to be in good condition, then could anyone tell me what might be causing these misfires and other errors?

  41. Slight misfire in my Chevrolet LS 2.2 liter HHR 2006 changed spark plugs but still a slight misfire should I change the whole coil pack

  42. Three months ago I had transmission lurching, engine overheating, and CEL  on load only. Radiator guy said I needed a new radiator; trans guy – trans work. Then I saw your vid. Went with your advice; checked coil packs, plugs & wires. It was # 2 ignition wire. New set of Delphi wires – $29. All problems ceased. Thanks, Scotty, for saving me tons of money – AGAIN!

  43. Scotty I have a 98 Nissan Frontier I have code p0301 thrown I’ve replaced plugs, plug wires and fuel injector still have the code throwing what would be next step to take

  44. Hey Scotty I been having an issue with my 2006 Dodge Charger,I keep getting a cylinder 2 misfire ,I’ve changed the ignition coil and plug ,but 3 or 4 days later the engine light comes on ,I scan and again cylinder 2 ,what is going on?

  45. he tells you alot bout cars i have learned a lot about cars here
    i like his video`s they are right and tells you the problem and how to fix them

  46. I have a 2012 Chrysler 200 it has the 3.6 L. Getting code P0304 I changed all the plugs made sure they were gap At 40,000’s is what they told me at the auto store they were supposed to be gapped at I change the injector in number four Cylinder and the coil and I’m still getting read out of number for misfire could you help me?

  47. Good God man!! There's an extension cord running right thru that pond you were standing in!! SMH!! LOL

  48. Had a P0303 and looked at the wire on cylinder number three and that was the issue. It had corrosion in the boot. I have been driving it for 6 months with a miss fire, but with your advice it was an easy fix, Thanks!

  49. 1999 Jeep XJ Cherokee:

    I've done all that, (actually had the p301 come up 1000miles or so after changing the plugswiresrotorcap) and the valve cover gasket (needed it anyway) and the injectors. The #1 injector actually did have a broken rubber O-ring at the engine side, so I thought I was fixing something! NNNyope! Any ideas what next to throw at it?
    The new injectors are 4 hole, by the way, replacing, probably original, 1 hole injectors. Since the behavior is the same, it is probably not an issue, but I mention it anyway.
    The check engine light will flash at highway speeds or sometimes accelerating from stationary. But only sometimes.

  50. Hi Scotty my wife has an 06 nissan sentra 1.8 that is missing and giving a code p0301 cylinder one misfire. I changed the plugs . The coil pack/wires seem ok . I swapped the coils to see if the miss would move to another cylinder but it did not. I listened to the injectors with a screw driver they sounded the same but I didn't test them or pull them and clean them. However a while ago I changed almost everything on it except the cats. So a week ago I changed the cats .After I changed the cats it smoothed out for a while but now it's missing again. for a moment it seemed smoother and the throttle response is back. But now it's missing again. I did break a bolt where the manifold fastened to the exhaust just before cat #1 .
    So will that cause the code I'm getting? Sorry for the long drawn out question but need some help.
    Thanks in advance.

  51. Scotty my 2017 mustang had engine light on! I took it to Ford and it said engine missfire! But the car runs fine so they took the engine light off and car is fine! What can cause it?

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