Any help would be greatful. I have a 2005 Dakota quad cab v8. Popping out code p0300 randon misfire. I have replaced all 8 coils, new egr valve, new tps,4 o2 sensors, and the code still comes up. usually acts up at start up under load at take off, acts like it will stall but doesn't, When I gas it hard it clears up and runs good. Any ideas of what could be wrong? Im leaning towards a vacuum leak.

 

random misfire would have me lean towards a computer issue (seeing as all the sensors have been changed) unless all your plugs are bad (didn't see if you changed those). If you have access to a scan tool you can watch and see which ones are misfiring and triggering the code. I wouldn't buy a computer without a little more research, you can go broke quick throwing parts at it, only to find a squirrel chewed a wire somewhere (don't ask how I know that)

 

One thing that you can also do is to clean your Throttle Body and do an application of seafoam. i prefer the spray can in the TB over the bottle through a vacuum line. I was surprised how dirty mine was, and i only have 50K KM on my 2011.

Could also be a fuel issue or even a dirty fuel filter. Also, check your air filter.

 

throttle body wouldn't cause a misfire code though

 

dirty throttle body, or dirty air intake, can cause a bad air/fuel mix that will not combust as good as the computer is expecting, causing a random misfire. If it was a misfire isolated in one or two cylinders, then i would not say throttle body. I'm not saying that it won't mix well, but it might not get enough air past carbon buildup until he mashes on the gas and opens up the throttle body more then it was at first.

And the seafoam doesn't just clean the throttle body, it cleans the whole air intake, the top of the valves and even helps clear out buildup in the Catalytic converters and cleans the O2 sensors. In his case the O2 sensors are new, so he doesn't need it. The misfire can be caused by many different things, you mentioned the computer, i'm just offering other suggestions based on my experience with my truck.

And i'm not saying that this is exactly what the issue is, but it is something to look at, above and beyond the other things that he's already done.

 

cat could cause it, but I have never seen a throttle body cause a misfire code, it would have to be almost solid. Does the light flash while driving? Do you let it sit and idle for long periods (like parked somewhere waiting on someone)? Could unhook exhaust and see if it goes away

 

Probably not your issue, but the last time I got random misfire codes, it turned out that there was moisture inside my coil pack not making a good connection with the spark plug. Blew it dry and sprayed on some wire dryer...no problems ever since.

 

depending on the mileage, normally a leaking headgasket will throw that code, is it only one cyl or a whole bank of them?

 

it does have all new plugs. did the seafoam thing a few times and problem still exists. only at start up. Head gasket is also good. the truck runs great after warmed up and running down the highway.The cat is also fine. Gonna try cleaning the injectors next. if they are clogged they could set off a random misfire code. will see what happens.

 

it flashes when I start to take off yes