Easy fix, remove the carbon buildup>> Misfire Due to Excessive Carbon On Top of the Valves or Sticking Valves.

 

have you done any work to the rotating assembly of the truck, transmission, torque converter, crank sensor, things of that nature?

What are the short term and long term fuel trims like, + or - 10 or more? A flashing check engine light usually means the trims are a good bit positive which may indicate a vacuum leak.

Neal

 

I just bought the vehicle, the price was right, the only things I’ve done are, spray brake clean around and inspect intake, replace all misfiring cylinder coils, replaced all wires, replaced all plugs and try to diagnose via my scanner for any potential irregularities, below are some screenshots of the fluctuations

 

P0300 shows up at idle> SES Light Misfire DTC P0300

 

thanks, that bulletin is very informative, there is no noise associated with it, maybe slight engine rattling noise, and I mean really slight, could be sticky valve(s), with mileage I wouldn’t be surprised if she’s caked with carbon throughout. I’ll have to check again tomorrow. But valve leakage section seemed to have the most comparable symptom. A previous owner along the line did do some work to it, as it does have new water pump, new exhaust manifold, some wiring repairs. So it wasn’t completely neglected, but that said it’s worth a deeper dive.

 

Start by adding Lucas into the tank(cheaper by the gallon)> Lucas Oil 10013 Fuel Treatment Gallon

 

I found this in picture form in a similar thread, would you by chance know how to navigate to the original? I’m new to the forums, its easy to get lost down the rabbit trail —I’m misfiring on the exact same cylinders and wouldn’t mind seeing the rest of the suggested procedures, there is still great throttle response, and no hard or long starts.

 

is your scan tool capable of special functions? you can try the crank relearn. maybe they have replaced the crank sensor previously without calibrating it using the procedure.

 

that I don’t know, it has capabilities to manipulate switches, electronic e-brake etc, , but it’s more of just an in depth scanner for diagnostic, rather then being a program or shop tool. I will check into that though because I feel maybe I did see an option for that .

i did read another post via google that was identical, every symptom, to a T right down to 6,8 showing the worse, but there’s still decent throttle response and only a slight feel of mis on idle, and they narrowed it down to what your saying about the crank sensor relearn.

the thing is, the past 2 days now, I don’t have that p0300 code, but I usually only drive 10 mins around town to take kids to school, go to store etc. However if I monitor the cylinders on my scanner, it is still indicating the misfires on 1,5,6,8, maybe just not enough to trigger the code. I’m also wondering if it sat for a while prior to me buying it, and maybe just needs good fuel, and driving to help clear it up.

 

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