Trouble shooting a misfire code P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308

hi my name is Robert this video is designed to give you step-by-step detailed instructions on completing the task at hand visit my youtube channel and watch my disclaimer video and please like share and subscribe I hope you find the information looking for thank you very much for watching lately I’ve been seeing a lot of information and questions about people having misfire codes some will do a little video to hopefully help you be able to deal with that and understand what’s going on with it first off any time your car is running rough shaking it idle seems to be vibrating the car idle more unlikely its misfire if a car has bad mounts or something like that that usually wouldn’t make it shake or vibrate at idle any times may tell me their cars shaking i right away know that it’s more than likely misfire this is normally also evident by a check engine light on your instrument cluster some people ride around with those lights on all the time something you really shouldn’t do because if another error happens in the system you won’t know about it because you’ve been riding around with a bad oh – error code so if at all possible if you can afford it when you can afford it get your car fixed so that you’re not riding around with the check engine light that way when things like a misfire occurs you have notification by the pointing of the misfire code pretty much this is the minimum things required to diagnose a misfire code I’d use a magnet and to pull spark plugs out of the wells because a lot of times your deep you got a socket spark plug wrench to get spark plugs out you got a compression gauge to check compression if you get that far you got a code reader to read the codes and you got gloves to protect your hand 99 times out of 100 you have a misfire code you’ll have a check engine light on your dash and you can stick your code reader into your obd2 port and second four codes and when you hit the scan and hit codes my car has no codes but usually it will say a code of P 301 or 302 or 300 300 however many cylinders you have most of the time it will point to the exact cylinder that has the miss fighter it’s not very common for you to have multiple misfires but if you do have multiple misfires that’s another issue so we’ll go ahead and cover some of that let’s just assume that I have a P 302 code which means that my number two cylinder is misfiring this is what my code reader looks like when it’s showing a misfire on number two yours may have more details and say misfire cylinder 2 and I’m a link a misfire troubleshooting video right here as well okay my car is a 5 cylinder and here you can see the intake manifold 1 cylinder 2 cylinder 3 cylinder 4 cylinders 5 cylinder you may have to look in your owners manual to see how your engine is laid out and where the cylinders are my number one is in the front up by the time we cover my number 5 is in the back by the distributor cap in the wires so if I have a number 2 misfire I have to pull this cover off of my motor and then pull my number 2 spark plug to see what’s going on in that cylinder now I’m not a hundred percent sure how it does it but somehow your car’s computer knows when it’s not firing all 5 cylinders it probably gets some kind of reading back from the spark plug wires or something letting this computer note that this engine is firing on all of its cylinders where the car needs to fire it needs fuel it needs air it needs compression and it needs a spark signal and a good spark plug to fire that off so if you’re having a misfire one of those things is not happening in that particular cylinder the cylinders not getting sparked it’s not getting enough fuel it’s not getting enough compression it’s not getting enough air or it’s not getting the right mixture of those things so when we try to diagnose a misfire we have to determine what exactly is going on in there occasionally I’ll have people ask well is my mass airflow sensor bad is that causing a misfire or is my fuel pump

going bad is that’s causing a misfire you know what exactly is it that’s causing a misfire well if you have one specific cylinder misfiring say number two then it’s not your mass airflow sensor it’s not your fuel pump it’s not some other common component because if a common component was going bad like your fuel pump or your mass flow air sensor which controls air going to the motor then you would have multiple misfires all the cylinders would misfire or something like that an example one time I had my car till today a crooked road well that was causing my fuel pump not to pick up my gas and my car was simulating running out of gas because it was running out of gas because of the way the car was tilted and I got a multiple misfire all of my cylinders misfired so I got the car flattened out the fuel started sucking back up in there and my misfires went away I cleared the code and I was fine and I got more gas in the car so that wouldn’t happen but if you’re having a specific misfire code you need to find out why now for the sake of speed and illustration I’m not going to do this but I would remove my spark plug cover so I have access to my spark plugs not all people are able to do this because sometimes spark plugs are under manifolds and stuff like that especially on your v6 in your v8 style cars but on my car I have easy access to all my spark plugs so let’s say I had a misfire on number two I pull my cover I pull that spark plug and what I want to do is look at that spark plug and see if that spark plugs look serviceable or if it looks damaged or if it looks like it’s not being functioned properly now when you pull the spark plug out of a motor this is kind of what you want it to look like not too much black around the top of it the tip of it seems like it’s in good shape then the very tip of it the arm that goes over isn’t all deteriorated and busted up so you want to make sure that the spark plug pretty much looks like this so it’s allowed to have some discoloring but to confirm that your spark plug is in good shape you can go to a website like a champion or NGK or something like that and look at the example of the spark plugs on their website so you can see the kind of condition you’re having with yours now if you’ve been running your car and you shut it off and the spark plug is wet with gas you can kind of guess that this spark plug was not being fired because it’s soaked with fuel now every car has spark plugs that have the specific gap it’s supposed to be the gap is supposed to be from the very tip of the core to the arm that goes over them now if for some reason you have special plugs that has multiple pins that come across there’s nothing you could do about the gap on those but if you have a spark plug like this platinum or double Platinum or regular copper tips you can measure that gap to make sure it’s within the specifications of your owner’s manual or the specification of some other kind of service manual that tells you what that gap is supposed to be if that gap is far off say for instance mind is supposed to be point zero three five and I measured in it’s point zero four or five it’s highly likely that the spark plug is worn or miss gap so that’s causing my misfire I just adjust this with my spark plug gap gauge so that I get back within the proper range so that the car will let that cylinder fire again so the first thing you want to do is pull the plug and check the spark plug gap and check the condition of the spark plug to make sure that is proper if the gap is wrong or the spark plug looks bad respect replace the spark plug clear the code start the car up drive at five or ten minutes and then recheck to see if your misfire comes back if your misfire comes back you need to go to step number two alright step number two you want to verify that your spark plug is actually sparking if you have plugs and wires like my car has an older car what I normally do is I disconnect my fuel supply I either pull my fuse for my fuel pump or else I will pull my fuel pump relay then I’ll pull the plug back out of the motor I hooked the spark plug wire up to the plug I’ll lay the plug close to a

bolt on the motor or lay it out across so that it’s sitting somewhere where I can see it I’ll crank the car or have somebody crank it and I’ll look in that gap to see if spark is jumping from this tip of the plug to the core to plug if I’m not getting any spark going into that plug or with the spark plug tester if you’re fortunate enough to have one of those then I know I got a problem either I got a bad spark plug wire or my distributor is bad now most of your cars newer then saved year 2000 they don’t actually have the distributor cap and rotor and wires that go over to spark plug that if that’s all more of an electronic system that’s controlled by the computer and they actually have individual pole packs bolted on top of each spark plug if you have that kind of system you have to unplug the coil take the coil off the spark plug just to gain access to the spark plug and then the best way to test the coil to see if it’s working in providing spark to the plug is let’s say your number two is misfiring I would take the coil off of number two and switch it with the coil on number three or number four or number five then I would bolt everything back together take the car for a test drive and when your check engine light comes back going I would read the code reader to see if the misfire moved with the coil swap so if the quarter was on number two and you put it on number five and now number five is misfiring I believe it is safe to say that you had a bad coil and you need to replace that coil go ahead replace that coil and make sure that the problem stays away and if it doesn’t we have to move to the next step now the next step in tracking down a single cylinder misfire is to check to see if that cylinder is getting fuel now if you pull that spark plug out and that spark plug was dry didn’t have no fuel on it there is a chance that hey you’re not getting good fuel from your fuel injector so you might want to check your wires going to your fuel injector but what I would do before verifying the fuel injector situation is I would check compression in that cylinder as I stated in the beginning of the video in order for a car to fire and have proper ignition every time it cycles it’s got to have good compression so what you want to do is you want to deactivate the fuel system again either fully the relay for the fuel pump or pull the fuel diffuse for the fuel pump deactivate the ignition system because you don’t want the ignition system sparking when you’re not going to run the car that way you can check your compression I have a couple of compression test videos that you can check into to see how to do a proper compression test but we’re just going to talk about it real quick and get that compression checked on that cylinder to see if that’s your problem why you’re not good fire and report misfires on that cylinder so you got your spark plug for that cylinder removed you got your fuel pump deactivated you got your ignition system deactivated either by disconnecting the lead off the coil or you pull some kind of fuse or relay or unplug the coil system so that your coil packs are not firing you pull that spark plug out you take the compression gauge and you screw it down in the hole that the spark plug comes out up you don’t have to screw it tight just hand tight is good enough it’s got a nice rubber seal on there to seal it off so it doesn’t leak air so now you go in the car you crank the car and you listen to it turn over about eight times ringa ringa ringa linga after eight times you stop you come back out you look at this gauge you need to find out with a good compression for your particular car on my car the compression is supposed to be between one hundred and fifty-six psi and 186 psi now if i hook this gauge up crank the motor over and my pressure is down around sixty for some reason I have bad compress in that cylinder now if that compression

is under sixty say it’s like 30 or less there’s a good chance that I have a burnt valve so if a car is burned the valve is going to have a misfire and that misfire is because you don’t have good compression so let me talk a little bit about burnt valves now if your car is got low compression in a cylinder the quickest way to determine if it’s a piston or valve problem is to pour a little oil down through the hole get the spark plug came out of there’s a piston under that spark plug that comes up and almost hits that spark plug to come to make compressed air so that when the fuel and the spark happens it creates a good explosion well in the case that you may have a bad piston or a bad piston ring you pour about an ounce of oil down that cylinder you can go two ounces if you want to go overboard you let that sit for about a minute and that’s about as much as a shot glass then you put the compression gauge back on it you crank it back up and when you crank it back up if your pressure went from let’s say 30 psi up to 150 psi or over 100 psi you know that that oil sealed up some kind of leak in Eric’s cabbage and the problem is with the piston but if that pressure is still real low around 30 somewhere around there where it was initially then you more than likely have a burnt valve now most of your modern car motors especially these overhead cam motors as you can see I have five cylinders and 20 valves so each one of my cylinders has two valves just two valves on the intake and there’s two valves on the exhaust now cars burn valves and what a burn valve meaning is is that this valve got so hot and the temperature was so extreme that it caused the valve to chip or crack or a little piece of that valve came off and it’s no longer there so when that valve is supposed to come back up and make a tight seal so that pressure could build in that cylinder air is escaping past that valve now some people say what causes a burnt valve the most common reason for burnt valve is internal oil leakage past the seal that is lubricated to help that valve go up and down the valve and the motor goes up and down rapidly as the motor runs and there’s little rubber seals at those valve stems these valve stem seals over the life of your engine they get hard and some oils is better than others in keeping them soft but if or you’ll start seeping by them because of their old and not condition then oil will settle on those valves and if those valves seat open a little bit when the engine shuts off that oil gets down on the tip of that valve and it cooks and crystallizes there well over time when the engine starts running that stops that valve from seating sealed closed when the motor is running and when the valve doesn’t closed off properly it causes it to get hotter and hotter and hotter let’s say these valves are supposed to be conditioned to take up to 900 degrees Fahrenheit well a valve that’s not seating closed properly because of this excessive oil leakage over time that valve may get to 1600 degrees or 1800 degrees and that extreme heat because it’s not sitting closed all the time will cause that valve to crack chip and break off now you have a burnt valve well sad to say that at burnt valve is just as bad as having a blown head gasket the motor has to come apart the valve has to be replaced the motor has to go back together normally with a new head gasket to fix the problem most of time people experience that problem they tear the head down and replace all of those seals to avoid that from happening again which it shouldn’t happen for a long time but nonetheless it’s normally an expense that sometimes exists exceeds the value of the car so that’s how you chase down a misfire if you got any questions go ahead and post them last but not least there’s a chance that you

have a problem with fuel delivery now if you check your compression and your compression is good the last thing I would check is fuel delivery and if you pull that spark plug out then it was dry and you’ve been having misfires there there’s a chance that you don’t have good fuel delivery so almost every car you deal with will have a fuel line that comes over to a fuel rail or two and when you look at the fuel rail let me pull this one off on these Volvo’s these rails just lift off and now you have access to each fuel injector two three four five the wires there you want to make sure that the wires are in good condition and you can make sure that the fuel injector down in there has a good seal into the motor now on my car I can disconnect this fuel line remove these two bolts and my fuel rail will lift off of this motor intake manifold I have to be careful I don’t damage my fuel line here that goes to my pressure regulator but once I get that fuel rail up I need to make sure that all the seals that seal the injector as they go into the motor are in good condition so there you see that a fuel injector going into the manifold and there are several of those that go into the manifold I have to make sure that those seals are good if one of those seals are bad it may cause a misfire because air pressure may be escaping the intake valves through that injector there also I want to make sure my wires are good and I want to make sure that injector fires so if I suspect I got a bad fuel injector I can untouched that injector move it over to the other position move that one over to that position start the car take it for a test drive read the codes if my misfire moved with my injector swap I likely have a bad fuel injector I can replace the fuel injector or take it to a shop somewhere that can see if it can be cleaned out and repaired now if you suspect that you’re having misfires because of fuel injectors being clogged you can sometimes run fuel injector cleaner through them to clean them up and get them from not being gummed up or whatever the problem is that’s causing them to not spray a good solid pattern of fuel into the cylinder so it can fire so there you have it you had a problem with spark you have a promo compression you have a problem with fuel delivery or you have a problem with an ignition coil or maybe even a spark plug I’ve even heard of people pulling the spark plug out our plan will be broken so I wouldn’t put it past even a sparkplug being broken but those are the steps going to take to figure out why you got a particular cylinder misfire if you got any questions go ahead and post if you feel that this information was beneficial please like it and share it with your social media friends you can also subscribe to my channel so that you can get notifications of future videos that I post visit my channel I have all types of do-it-yourself videos there you can leave questions here and I’ll try to respond to them as quick as possible you can also visit my website at Robert thanks again for watching