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Engine misfire. How to fix a random misfire in your car DIY with Scotty Kilmer. How to stop random engine misfire code P0300 with check engine light on. Engine randomly misfires inspection, troubleshooting and repair. DIY car repair with Scotty Kilmer, an auto mechanic for the last 42 years.

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45 comments on “How to Fix a Random Engine Misfire in Your Car (Code P0300)

  • I currently own a 97 lumina, and it’s been throwing off a random misfire. I just replaced all the spark plugs, wires, battery, and coils before the code started. I currently am in the mist of changing the EGR valve. There no leaking from anything either. so what could it be!!??!!?

  • A couple months ago I had transmission lurching, engine overheating, and CEL  on load only. Called radiator guy. He said I needed a new radiator. Called trans shop, he said it was the torque convertor. Then I saw your vid on misfires. Stayed away from those shops & followed your advice; checked coil packs, plugs & wires. It was # 2 ignition wire. Got a new set of Delphi wires for $29 and all three problems ceased. Thanks, Scotty, for saving me tons of money & aggravation again.

  • I'm having an unusual misfire. No error code or check engine and I had 4 mechanics take a look and no one can figure it out. All the main gaskets were replaced, fresh oil change and new spark plugs but still a random misfire here and there. any advice please ?

  • I got a missfire at iddle and between 40 to 50 mph no codes 98 chevy blazer lt running denso platinum sparkplugs and using duralasst wires. Everything else is delco,fuel pressure is good.

  • Hey Scotty my partner has got a cx7 2008 turbo over 200,000kms on it and its having a bad jerking problem upon acceleration the engine light flashes then it stays on I checked the codes all it says is cylinder 3 misfire so I changed the spark plugs problem still there I changed the coil in cylinder 3 to cylinder 4 still having the same problem so I cleaned out the throttle body made no difference do u think it could be the fuel injector ? What else could be the problem?

  • my moms 2001 toyota tundra has the CEL flashing and shaking. she told me that at idle there's nothing but when you put it in drive it starts shaking and smooths out as you accelerate, but when you brake the shaking gets really bad. if you know any more about this and possible causes and what it could cost to get fixed please tell me.

  • My last random/multiple misfire was a bad engine with cam failure. 8 months later I'm dealing with the same codes, hope it's not the same thing or it'll be the last hemi I ever get!

  • Hi Scotty , I putted in a new head gasket cause my mechanic said he found coolant in cylinder 3 and 2 because I was loosing coolant but there was no leak anywhere so he said the headgasket was bad ,so after it was done
    I was still having at hard start on the first cycle,
    Then I went back to talk to mechanic and he said it might be the ECU because there was no engine light to see what was going on with the car.
    So coming home after talking to him the engine light came on and I got these codes , p0302, p0303, p0300 and the famous p1399
    What should I do now?

  • 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?

  • Corrosion on coil pack terminals and all spark plug terminals are rust pull out plugs and grind off all corrosion use dielectric grease on terminals not to much grease or else wires will pop off when engine is revving dont over grease!

  • Po300, 05 Chevy Impala. Seemed to happen right after filling up with Costco gas. Could bad gas cause a random misfire?

  • Hello Scoty 🙂
    I'm owner on Fiat Punto mk2 1.2 8v car. Last time i got problems with misfires.. And im suspicious on the coil packs.
    So i do multimeter test:
    On the Ht input resistance test i'm getting 2.6ohm and 2.8 ohms on the other coil..
    On the HT output resistance test, i'm getting 7.4 kohm and 7.3kohm..
    What means this result?
    And also when i tried to measure continuity on the HT output pin there was no result.. number 1 was on the screen nothing else…
    Can you help me? 🙂

  • CODE 300 showed up on my 2005 sentra 1.8. problem … in the morniNG it cranks over a few seconds then sputters a few seconds then smoothe great. , I unhooked the neg bat let it sit a few hours , hooked it back fired right up … After I run the run dog crap out it fires up great . I paied a mechanic 300 dollars to test it , replace the plugs. a few days latter same s..t different day .. HELP . THANKS.

  • I have 92 corolla and it was not working. The local machenics diagnosed and said – oils burned out the engine. Probably engine was too low and burned the engine off. I showed to 2 other machenics , off the record &they said the samething. Do u think putting a new engine would require a new dark plug? Right now it's not working even though new engine is installed.

  • On my daughter's 2000 Pontiac Grand Prix it needed a new battery, spark plugs and wires. Two of the spark plug wires were broken. The car had the original wires. Running like new now. I had a mechanic do the spark plugs and wires though.

  • 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?

  • Scotty,

    I have a 2006 Toyota Sienna with 105,000 miles. Used to get jerky random misfires any time I stepped on the gas. I replaced MAF sensor with denso, all 6 spark plugs completely worn down and replaced with ngk, replaced cylinder 2 coil with denso (it was bad), and fixed a frayed fuel injector wire on cylinder 6. I also found a flex pipe exhaust leak after cat 1. That will be fixed next week. Still the car jerks and random misfire flashing cel any time I go above 4000rpm but it runs great now up to that rpm. You think the exhaust leak is causing all that or I still have issues? Crank sensor maybe? Only code I've ever gotten are p0300 and the p0302 was fixed with the new coil. Thanks!

  • Thank you sooooo much scotty,my toyota corolla 2001 has been giving me this issue and also stalls ….i have checked everything now i think i need to check the battery …
    thank you soo much

  • Good video. Turns out my voltage regulator (2002 silverado 5.3) was not charging properly…aka multiple misfures due to lowered voltage in the system. Thanks!

  • Scotty is a G he just makes it look ao easy you ask other people first thing thay say you better get another car. LOL

  • You forgot EGR valve hanging open which is a very common cause of engine misfire especially multiple miss fires. The carbon build up can cause the valve to stick open sucking in air and changing the air to fuel ratio. I went nuts for months trying to find the issue on a Honda Civic. Come to find out when unplugged the egr the car ran like new! So went and pulled the old one. Sure enough, clogged solid. I replaced it and plugged it back in. All is well.

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