Please help! p0306 code drama
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Please help! p0306 code drama
Truck: 2019 F150 5.0 with 160k on the clock.
Issue: Check engine light on. Truck runs extremely rough at idle and misses all the way up to 2500 RPM. Codes p0306, p0300, p0316 and occasionally p0302 (but not always). I can clear the codes with forscan and they will come back after a few minutes. It started after a full throttle pull one day to pass someone, but then came and went until now its permanent. Truck does not burn oil, runs great when the misfire clears up around 2500 rpm.
What I have done so far: All new motorcraft spark plugs. New motorcraft coil for cylinder 6 (have moved it to other cylinders also with no change, misfire remains in cylinder 6). Moved port fuel injectors around on bank 2, with no change. Installed new motorcraft vct intake solenoid on bank 2. Using forscan I monitired the fuel injection, the misfires only happen while the truck is running on port fuel injection, not when its on direct injection.
Obviously I have access to forscan and have a shop with tools (I am a mechanic, just not a ford mechanic!)
Thank you in advance,
Josh
Issue: Check engine light on. Truck runs extremely rough at idle and misses all the way up to 2500 RPM. Codes p0306, p0300, p0316 and occasionally p0302 (but not always). I can clear the codes with forscan and they will come back after a few minutes. It started after a full throttle pull one day to pass someone, but then came and went until now its permanent. Truck does not burn oil, runs great when the misfire clears up around 2500 rpm.
What I have done so far: All new motorcraft spark plugs. New motorcraft coil for cylinder 6 (have moved it to other cylinders also with no change, misfire remains in cylinder 6). Moved port fuel injectors around on bank 2, with no change. Installed new motorcraft vct intake solenoid on bank 2. Using forscan I monitired the fuel injection, the misfires only happen while the truck is running on port fuel injection, not when its on direct injection.
Obviously I have access to forscan and have a shop with tools (I am a mechanic, just not a ford mechanic!)
Thank you in advance,
Josh
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Joined: Mar 2021
Posts: 4,789
Likes: 2,390
Here is what the situation is according to the codes.
300 and 316 are telling you the same thing. Misfires on startup.
302 & 306 are on opposite banks so they are not in common except to misfiring from the root cause.
Conclusion: It's not the plugs or coils.
You' need to take a look at fuel pressure before cranking and at crank starting to see it there is a problem with being too low on fuel pressure and what the high pressure goes up to.
Once the engine is running it's on the DI injection 100%.
If you can look at both port and direct injection at the same time, you will see the port inj. being opened if you jazz the throttle. If they don't, even this can cause poor performance due too going too Lean for that instant trying to add additional fuel when commanded.
.
Something else in the mix.
At startup, the PCM goes into an Emiussiins test of the CATs.
Low fuel and faults will interfere with testing, as well.
A good Scanner is invaluable for looking at these kinds of issues set up in Live data monitoring for all the parameters involved, to see the root cause.
.
Good luck.
300 and 316 are telling you the same thing. Misfires on startup.
302 & 306 are on opposite banks so they are not in common except to misfiring from the root cause.
Conclusion: It's not the plugs or coils.
You' need to take a look at fuel pressure before cranking and at crank starting to see it there is a problem with being too low on fuel pressure and what the high pressure goes up to.
Once the engine is running it's on the DI injection 100%.
If you can look at both port and direct injection at the same time, you will see the port inj. being opened if you jazz the throttle. If they don't, even this can cause poor performance due too going too Lean for that instant trying to add additional fuel when commanded.
.
Something else in the mix.
At startup, the PCM goes into an Emiussiins test of the CATs.
Low fuel and faults will interfere with testing, as well.
A good Scanner is invaluable for looking at these kinds of issues set up in Live data monitoring for all the parameters involved, to see the root cause.
.
Good luck.
Thread Starter
Junior Member
Joined: Aug 2025
Posts: 9
Likes: 5
Here is what the situation is according to the codes.
300 and 316 are telling you the same thing. Misfires on startup.
302 & 306 are on opposite banks so they are not in common except to misfiring from the root cause.
Conclusion: It's not the plugs or coils.
You' need to take a look at fuel pressure before cranking and at crank starting to see it there is a problem with being too low on fuel pressure and what the high pressure goes up to.
Once the engine is running it's on the DI injection 100%.
If you can look at both port and direct injection at the same time, you will see the port inj. being opened if you jazz the throttle. If they don't, even this can cause poor performance due too going too Lean for that instant trying to add additional fuel when commanded.
.
Something else in the mix.
At startup, the PCM goes into an Emiussiins test of the CATs.
Low fuel and faults will interfere with testing, as well.
A good Scanner is invaluable for looking at these kinds of issues set up in Live data monitoring for all the parameters involved, to see the root cause.
.
Good luck.
300 and 316 are telling you the same thing. Misfires on startup.
302 & 306 are on opposite banks so they are not in common except to misfiring from the root cause.
Conclusion: It's not the plugs or coils.
You' need to take a look at fuel pressure before cranking and at crank starting to see it there is a problem with being too low on fuel pressure and what the high pressure goes up to.
Once the engine is running it's on the DI injection 100%.
If you can look at both port and direct injection at the same time, you will see the port inj. being opened if you jazz the throttle. If they don't, even this can cause poor performance due too going too Lean for that instant trying to add additional fuel when commanded.
.
Something else in the mix.
At startup, the PCM goes into an Emiussiins test of the CATs.
Low fuel and faults will interfere with testing, as well.
A good Scanner is invaluable for looking at these kinds of issues set up in Live data monitoring for all the parameters involved, to see the root cause.
.
Good luck.
Thank you sir, working on it some more this afternoon. I guess I was confused on the port and direct injection, but when I pulled it up on forscan, it was showing port at idle and low input and then it would go to direct when I gave it some go juice. I am going to try getting some readings on fuel pressure. Also, arent you the guy that said to do the liquimoly additive for oil consumption? If you are, thank you. This one burnt a little oil when I first got it, so we have dumped in a bottle of the liqui moly at each 5k oil change and its been perfect.
Thanks!
Josh
Thread Starter
Junior Member
Joined: Aug 2025
Posts: 9
Likes: 5
Here is what the situation is according to the codes.
300 and 316 are telling you the same thing. Misfires on startup.
302 & 306 are on opposite banks so they are not in common except to misfiring from the root cause.
Conclusion: It's not the plugs or coils.
You' need to take a look at fuel pressure before cranking and at crank starting to see it there is a problem with being too low on fuel pressure and what the high pressure goes up to.
Once the engine is running it's on the DI injection 100%.
If you can look at both port and direct injection at the same time, you will see the port inj. being opened if you jazz the throttle. If they don't, even this can cause poor performance due too going too Lean for that instant trying to add additional fuel when commanded.
.
Something else in the mix.
At startup, the PCM goes into an Emiussiins test of the CATs.
Low fuel and faults will interfere with testing, as well.
A good Scanner is invaluable for looking at these kinds of issues set up in Live data monitoring for all the parameters involved, to see the root cause.
.
Good luck.
300 and 316 are telling you the same thing. Misfires on startup.
302 & 306 are on opposite banks so they are not in common except to misfiring from the root cause.
Conclusion: It's not the plugs or coils.
You' need to take a look at fuel pressure before cranking and at crank starting to see it there is a problem with being too low on fuel pressure and what the high pressure goes up to.
Once the engine is running it's on the DI injection 100%.
If you can look at both port and direct injection at the same time, you will see the port inj. being opened if you jazz the throttle. If they don't, even this can cause poor performance due too going too Lean for that instant trying to add additional fuel when commanded.
.
Something else in the mix.
At startup, the PCM goes into an Emiussiins test of the CATs.
Low fuel and faults will interfere with testing, as well.
A good Scanner is invaluable for looking at these kinds of issues set up in Live data monitoring for all the parameters involved, to see the root cause.
.
Good luck.
Senior Member
Joined: Mar 2021
Posts: 4,789
Likes: 2,390
Too much Fuel Pressure?
No, here is why.
At initial Ignition on, only the tank pump is running. It's not capable of pressures munch over 100 PSI or (689 Kpa)
Normal regulated Psi should be in the 60 + PSI range to feed >>Port<< injectors for starting and emissions reduction.
.
After starting, the pressure should begin to rise to over 1200 Psi as the low-pressure system feeds the high-pressure fuel pump boost the pressure for the direct injectors.
At this point, fuel injection transfers from Port to mostly DI injector that need the higher pressure.
Note, the high pressure can go as high as 3000 PSI or 20684 Kpa.
Part of the fuel pressure action is used for the emissions test done at every startup. This is when you see the engine Idle speed rise into the 1200 rpm +/- range and hang there for a few minutes then slowly come down to the 600-rpm area. The test sequence is testing the CATS ability to heat up within a specified amount of time to pass or fail limits.
All this is normal actions.
Good luck.
No, here is why.
At initial Ignition on, only the tank pump is running. It's not capable of pressures munch over 100 PSI or (689 Kpa)
Normal regulated Psi should be in the 60 + PSI range to feed >>Port<< injectors for starting and emissions reduction.
.
After starting, the pressure should begin to rise to over 1200 Psi as the low-pressure system feeds the high-pressure fuel pump boost the pressure for the direct injectors.
At this point, fuel injection transfers from Port to mostly DI injector that need the higher pressure.
Note, the high pressure can go as high as 3000 PSI or 20684 Kpa.
Part of the fuel pressure action is used for the emissions test done at every startup. This is when you see the engine Idle speed rise into the 1200 rpm +/- range and hang there for a few minutes then slowly come down to the 600-rpm area. The test sequence is testing the CATS ability to heat up within a specified amount of time to pass or fail limits.
All this is normal actions.
Good luck.
Last edited by Bluegrass; Aug 24, 2025 at 03:39 AM.
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Still hunting for the fix for this gigantic POS. Valve springs are fine, injectors are fine, coils are fine, plugs are fine, vvt solenoids are new. IMRC functions correctly. I just have no idea at this point.
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It may be that the Crank Sensor needs to be re-calibrated in program for Neutral Re-learn.
This is a dealer only action or a few high-end Scanners that has that ability. Forscan does not have the ability, so an inquiry says.
If you check out about the Neutral Re-Learn on Ford engines, it will tell about the same possible misfires and codes being experienced by users in this thread.
Good luck.
This is a dealer only action or a few high-end Scanners that has that ability. Forscan does not have the ability, so an inquiry says.
If you check out about the Neutral Re-Learn on Ford engines, it will tell about the same possible misfires and codes being experienced by users in this thread.
Good luck.