Why Do Engines Misfire, Code P0301 (Compression Test)

Scotty Kilmer, mechanic for the last 45 years, shows how you can discover why your engine is misfiring and turning the check engine light on. If your vehicle has a misfire code, like P0301, stored in memory, there can be many different things causing this. Learn how to figure out the cause quickly by watching this video.

Things I used in this video:
6. Common Sense

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[scottykilmer]

Things I used in this video:
6. Common Sense

🛠Check out my Garage to see what I use every day and highly recommend:

❗️Check out the Scotty store:

👉Follow me on Instagram for the latest news, funnies, and exclusive info / pics:

[FacelessPimp]

Lol I love your energy. It makes me less upset about my cylinder misfire.

[wutangoc]

Your videos has kept my $150 pathfinder running like a champ with over 255k on it, so far I've only down routine maintenance like breaks, shocks and tires.

[scottykilmer]

to each his own, just realize I've been working on em 45 years and know which ones break down a lot and which ones don't.

[scottykilmer]

yes, try cleaning the intake out with cleaner and pray it unsticks.

[bhstone]

Scotty, you write like you talk. When I read your comments I can hear your voice in my head. It's amazing! Thank you!!

[scottykilmer]

check the wiring to the plug, pray something's bent or shorted out. If not, a bad main computer often will cause that, or a shorted out sensor anywhere on the computer sensor system

[scottykilmer]

yes, fluid expands from heat, and will move upwards as it heats up due to expansion.

[scottykilmer]

the ignition is disabled on that model as soon as you remove the coil assembly to get to the spark plugs. And you can check compression with throttle open or closed, doesn't really matter, it's only the pressure difference that really matters.

[scottykilmer]

yes, you can have the cat pressure tested for back pressure using exhaust gas gauges to see if it's clogged

[scottykilmer]

make sure you have the right spark plugs that are gapped correctly first. And if you cracked any plugs putting em in, that will do it for sure, take em all out and check for cracks in the porcelin

[scottykilmer]

air flow often is changed on new heads, so they will often suck air differently and make such whooping noises, I see that a lot. if it runs fine, it means nothing. But often cleaning the throttle can stop it if build up is causing it.

[scottykilmer]

it was for this one, but I've seen some with 200 thousand on em and still running, though they weren't Ions, they were earlier ones. Ions pretty much finished off Saturn as a maker.

[scottykilmer]

you do a leakdown for a more complex analysis. this shows an internal problem, and on this junker saturn the owner was going no further so it was good enough.

[scottykilmer]

many things cause misfire on those, but vapor coming out the back is generally leaking fuel injectors, or a blown head gasket. Do my test "how to tell if your head gasket is blown" first

[scottykilmer]

often it's actually bad fuel injectors or the lines that feed them, all plastic parts on that. BUT, if they were all changed, intake vacuum leaks can do that. See my video "finding engine vacuum leaks with a cigar"

[scottykilmer]

that's the code for engine position problem bank one. It means the engine has a mechanical problem somewhere on bank one of the engine, the bank that includes the number one cylinder (that's how they label them). good luck on that one

[rroge]

Its my favourite thing to see a new scottykilmer video

[Rinyotsu]

It'd be cool to get your input on this suggestion Scotty, so that I'm not just a random person with a random tip promoting some "miracle fix" product. Heck, even if you know some big problems with restore, I'd like to hear them! Thanks for your time Scotty and thanks for all the videos you make! You've saved me thousands!

[scottykilmer]

check the belts of course, and check what they drive, such as water pumps and alternators. Sometimes removing the belts and hand checking the pulleys will find the problem