When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I had a low coolant level displayed after leaving the house it was a radiator leak . After replacing with a new radiator I'm getting P0300 , have cleared the code 2 times so there a problem and checked spark plug wires but the code returns , no other code has of yet. So far it throws the code at start up.
Likely not related to anything with the radiator. Is the car running rough at all? Check your plugs and see if any of them look fouled. P0300s can be a pain to track sometimes and can be caused by a multitude of things. Start with the basics and check the plugs, may as well change them while your there. If that doesn't show anything the next step is to take it somewhere that has a scanner and see if you can track the misfires to atleast get an idea what your dealing with or see if its a specific cylinder missing. (typically even if its an isolated cylinder thats having the issue it will still kick a p0300 rather than a p0301-2-3 ect. I had a lifter fail on cyl 1 and it only ever through p0300 even though the hole had a dead miss. Best thing to do is get a scan tool on it and see if you can atleast identify where your problem is then start diagnosing from there.
Without a scan tool to see which cylinder is misfiring these things can be difficult to diagnose…mechanical, fuel, or spark…you can do a “clear flood crank” which is putting the gas pedal to the floor and keeping it there while attempting to start the car…the engine will only crank (injectors shut off) and should have a nice even cranking sound…this generally can rule out “some” but not all mechanical issues…what part of Florida ??…if you’re near to me in the southwest part I can take a look at it for you…if your in the southeast I know of 2 good diagnostic shops that can definitely diagnose it for you…those 2 shops and myself use advanced testing methods especially on the mechanical aspect of misfires where a normal shop will charge a ton of money in engine disassembly where our methods require none…did the engine ever overheat and is the coolant level still low ??
Wow !!…look at all those misfires…a bad crank sensor can cause the engine to run poorly and it’s also the ECM’s misfire monitor…can you do a crankshaft variation relearn with your scan tool ??…don’t know which one you have but if it’s a bidirectional one the test should be under special functions menu…it also looks like a majority of the misfires are on bank 2…look at your O2 sensors and fuel trims and see if the upstream sensor is “stuck” high (above 450mv)…if the sensor is bad it will “pull fuel” and you will have a lean misfire…sometimes the “companion cylinder” of the misfiring cylinder will also show a misfire because that companion cylinder is decelerating as well which the ECM will interpret as a misfire !!
Not familiar with that scan tool but looks like it has a “generic OBD2” function… go into that and look at Mode 2 or “freeze frame data” and see when the misfires occurred…the ECM takes a picture of the data when it occurred…this helps in a diagnosis !!..if your car is an auto you can “brake torque” it and see if the misfires are counting up…set E brake and with your left foot on the brake give it some gas with your right…you basically want to put a load on the engine.
The O2 are switching fine but if this is something you want to tackle yourself start with plugs and wires…anything beyond this is going to require some specialized equipment to accurately diagnose without changing a bunch of parts…I’d clear the codes, power brake it if you can and see who’s now misfiring while watching scan data…it’s cheaper to pay for an hours diagnostic fee than wasting your money shot gunning parts…single cylinder misfires are a little easier to diagnose but multiple cylinders can be a challenge…one shop is in Melbourne and the other is in Oakland Park north of Ft. Lauderdale if you want a pro to look at it.
Ok so try that and see what happens…if plugs are so so they usually misfire under a heavier load because of the higher cylinder pressures…plugs may fire good at idle but not so good under a load…if all those misfiring cylinders were all counting up on the scan tool that engine would be running poorly…could be a crank sensor but this is only a guess…I don’t like to guess…LOL !!
Changed the sparks plugs and wires this morning car started up good and ran for a few mins monitor showed no misfires , then shut it off 2-3 mins and restarted it no code yet but not had smooth and I can again start to see the misfires count.
So it's still misfiring ??...sorry to hear that if it is...if I were you I'd tap out and pay for an hours diagnostic and get it resolved quickly...if not I guess it's time to change some more parts...you can try injectors and crank sensor...like I said try a quick "clear flood crank" and maybe that may lead you to a possible mechanical issue...it's a little difficult to diagnose a misfire for you over the Internet.
No help just knowing there are just misfires…have to find the cause…that is a little more difficult without specialized equipment…your only option is just to replace parts and hope for the best…hopefully it’s nothing electrical which can make it more difficult to diagnose !!…don’t know what other help I can offer.
Trying to see what other test I can run to try to narrow down the possible problems, The good shop I went a few times moved so it will be hard finding good help , will try to see if someone can help with a Cylinder Compression test.
I would think it should have more misfires under load , seem like there are almost no misfires under-load driving (5 counted in 3.5 + miles ) VS idle or parked (127 counted) in that drive. What is stopping the misfire when the engine is under-load driving. I know it shouldnt have any misfires , but the different is high
Trying to see what other test I can run to try to narrow down the possible problems, The good shop I went a few times moved so it will be hard finding good help , will try to see if someone can help with a Cylinder Compression test.
I would think it should have more misfires under load , seem like there are almost no misfires under-load driving (5 counted in 3.5 + miles ) VS idle or parked (127 counted) in that drive. What is stopping the misfire when the engine is under-load driving. I know it shouldnt have any misfires , but the different is high
Like I mentioned to you try a "clear flood crank" and if you have a good ear you may pick up an abnormal cranking cadence.
Already did it "clear flood crank" , sound normal to a none pro ear , changed plugs , wires , switched coils with another LS3 engine and changed o2 sensors , most of the misfire are also on bank 2 on Cylinder 3 being the worst by far. Will try to see if someone can help with a Cylinder Compression test and test fuel Psi and check the valve spring.
P0300
