How To Fix A P0300 Random Cylinder Misfire

All right, today i’m gonna be diagnosing p0300 which is a random cylinder misfire on this buick Basically a problem with a p0300 random cylinder misfire is it doesn’t tell you It doesn’t identify, which cylinders are actually misfiring, so i’m gonna show. You how to check these, with i’m gonna show You, how to check the misfires with a scan tool, and also how to manually test to find out, which cylinder is actually misfiring so You can, repair it i’m working on a six cylinder here so basically out of the six cylinders, we need to figure out Which one of the ones are misfiring because the colored we’re getting, isn’t identifying the actual misfire it’s just a random misfire so Let’s just double-check that trouble codes here and as you can see We have the p0300 engine misfire detected So that doesn’t really give us a whole lot of information there it just tells us that, we have a misfire So i’m gonna go into the tech 2 here we’re gonna go into special functions and see if Miss paragraph so, we got a. Misfire graph here and hopefully this this is going to identify, which cylinders are misfiring so i’ll go ahead and open that up and All right this thing up and it is definitely misfire i can, feel it and as you can see we got cylinder six And cylinder three are misfiring so on this particular vehicle it’s got three ignition coils two coils that run Or three ignition coils, each coil runs two cylinders so it’s a six Cylinder it’s got three coils, each coil runs two cylinders so first thing i’m going to check up i’m gonna go under the hood and see if Cylinder six and three are Running, off the same ignition coil, which There’s a good possibility of the our clothes are pretty common on these but let’s go ahead and go Underneath the hood here and dig into this thing a little deeper now that we’ve identified Which cylinders are actually misfiring on this one it’s going to be six and three Okay, and here we have cylinder six? And cylinder three and as you can see these cylinders are firing off the same ignition coil so I’m just going to go ahead and start this thing up and see if we have spark coming out of the six and three ignition coil And to, do that all i’m going to do, is take pair of pliers and pull the wires off and as you can see there we got a nice strong spark coming off the cylinder and so the three, we have nothing and cylinder two, we have nothing So at this point and you want a nice strong spark like, you can see Yeah, pull out that one now, and actually almost all the motors so but so we definitely have No, spark coming out six. And three so on that’s what’s causing our misfire So at this point what we’re gonna have to do is our share, gonna swap these coils around because i Mean i’ll first First thought you would think that it’s a Bad ignition coil but on this motor and a mesa is actually the ignition module so each one of these coils has a driver That the ignition module powers So to verify Whether or not the ignition module is bad in this or if the ignition coil is bad We’re going to have to i’m gonna go ahead and swap Swap it with the Cylinder to five coil, which we know is working properly? Just to make sure the driver in the ignition mazal module hasn’t failed Also, another quick tip is when you’re pulling, these, spark plug wires off to check for spark If you’re, using a pair of pliers and you, don’t want to shock yourself a good, way to avoid, that is just take a? Take a little jumper and connect it from your pliers to a ground source and it’s that ignition spark Transference to the pliers it’s just gonna read redirects rate to ground so you, won’t get shocked also if you’re, wearing rubber gloves that will help and Before you start the motor you just want to make sure the spark wires themselves you know You’ve already loosened up, along up a little so you, don’t have to tug hard, on with the pliers because you Don’t want it’ll cause any damage to him So now, what i’m gonna do i got both these loosened up on this motor it’s just a, five point five millimeter Socket i’m gonna, swap the wires around and I’m gonna, swap the coils i’ll also leave a link in the video description below to Tune up stuff you can, buy on amazon i find that the cheapest and the fastest for shipping Yeah, and underneath these coils is actually two, little prongs that sticking there from the ignition module that actually drives the coils so basically by switching these like i said we’re gonna be Testing to make sure the ignition module is driving the coil properly So let’s fire we know for sure we had no spark on so under six and three which is causing the p0300 random cylinder misfire so we’ve narrowed it down to what cylinders it is We’ve identified it was no spark coming out of that coil And now, we have swapped the coils to make sure that our ignition module is right so i got these vicious Well swap i got the wires swapped around we’re gonna go ahead, and fire this back up and we’re gonna use the same test to, see if we have spark All right so we’ve got no spark now on the On this coil, we just walked, and the one that, we did have sparked didn’t have spotted before is now sparking So in this case the actual driver and this ignition module has failed so our coil is good Under the first assumption you would have suspected that this coil, was bad but now. By swapping this we have verified and now that the ignition module and this is actually bad and that’s what’s causing our p0300 Now if you’re getting a p0300 and you can’t Identify, which cylinder is misfiring with a scan tool or other ways, these are the best Ways just to come out and you know start pulling pulling wires and see which cylinder is affected by you pulling those admission wires off in this case it was pretty obvious to us that, we had no spark out of six and three and you know we’re, we were able to narrow down relatively quick Now in order to? Repair, this vehicle or, ask, well all three of these coils off and replace the module that sits down underneath it now probably Also, gonna replace the ignition coil Only, because typically i mean there’s a reason, why, these parts fail the This, ignition coil, could be shorting i mean it could have, some razak, high resistance and the primary windings and over time it could Have just stressed that that admission module so i mean inspect the rest of the ignition components on this vehicle Spark plug wires spark plugs themselves and if those all look, good we’re probably gonna, we’re gonna have to replace the ignition module and we’re probably, gonna be end up replacing at least that one ignition coil Buy-down, what’s actually failed in our case here is the ignition module Once again thanks for watching hope, this video Was helpful on p0300 random cylinder misfire be sure to hit the thumbs up button, below And subscribe to my channel says, was helpful thanks flat rate mechanic

Bernard Jenkins


  1. A timing light can uncover misfiring wires and coils and plugs. Spark plug wire pliers can be used.

  2. 8.2.2019
    Long Beach, CA.

    I wouldn't have swapped the 1st "2" Coils since thêre was No Spark coming from the 1st Coil ( #3, #6 ) & that would have bêen a mistáke.

    You did the right thing. Why ís that ?
    Because after implemnting thís Step, my Memory came back :
    The RPM Sensor turns on the Module
    The Module turns on the Coils
    The Coils Fire the Spảrk Plugs

    This time, the Swap showed that the Ignition Côntrol Module ís the Fault.

  3. Hi , my Audi A3 8l, 1.6 benzine 2001 misfire on sunny day. Other day , it won’t misfire. Any idea please??

  4. I appreciate the help thanks, feels good to know there's still some good people around .

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