Throwing P0300 code

[fjwlobo]

Had a 1980 Mustang that had a bad coil (when only one was needed). It would run fine when it first started, but after it ran for a while the engine would die. If I let the car sit for a while it would start right up. After it happened a few times I figured out what the problem was, replaced the coil, and off I went ? until the floorboards rusted out ?.

Basically, the coil had a break in the winding and once the coil heated up the winding would break connection and stop working until it cooled down.

As the Ranger has a coil for each cylinder it wouldn't die, just run rough. This MIGHT be your problem as stated earlier in the post.

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[JHC14]

Had a 1980 Mustang that had a bad coil (when only one was needed). It would run fine when it first started, but after it ran for a while the engine would die. If I let the car sit for a while it would start right up. After it happened a few times I figured out what the problem was, replaced the coil, and off I went ? until the floorboards rusted out ?.

Basically, the coil had a break in the winding and once the coil heated up the winding would break connection and stop working until it cooled down.

As the Ranger has a coil for each cylinder it wouldn't die, just run rough. This MIGHT be your problem as stated earlier in the post.

I am hoping...kinda leaning this way. Although mine does just the opposite. It seems to run rougher when cold and then smooth out when it gets warm.
I think when I get back from vacation next week, I will try replacing the coil packs and see what happens.
Rockauto.com seems to have the best price on them.

Does brand matter on these? There is the Motorcraft brand and then others I have not heard of. Any suggestions or recommendations?

 

[Techcargt]

I am hoping...kinda leaning this way. Although mine does just the opposite. It seems to run rougher when cold and then smooth out when it gets warm.
I think when I get back from vacation next week, I will try replacing the coil packs and see what happens.
Rockauto.com seems to have the best price on them.

Does brand matter on these? There is the Motorcraft brand and then others I have not heard of. Any suggestions or recommendations?

Get the motorcraft ones from RockAuto. The other brands can be of questionable quality.

 

[Techcargt]

And don't forget to get the ignition coil boots also motorcraft brand.

 

[airline tech]

So, if I understand correctly, you replaced the plugs as precautionary with a noted presence of water infiltration into #4 plug well.
Truck was running rough after this - Was it running rough BEFORE this?

6-Weeks and 8,000 miles - Light comes on and scanned - showing P0300, with a noted runs rougher when cold vs operating temp
You have replaced the DPFE sensor - was there any noted difference in driving after replacement?

I would not waste the money - throwing parts at it.
As the unknown is - Is it related to the Plugs / Coils or EGR or another area of concern.

The truck needs a scanner hooked up to see which cylinder or cylinders are registering the misfire.
This can be done with something other than a Code Reader; you need to view Live Data / Freeze Frame Data & Mode 6 Data.

There are a number of Live Data - PIDs to look at, Fuel Trims, EGR PIDs, O2 Sensor, Fuel Pressure, Map and Misfire Counter along with the Knock Sensor
another thing that can be done is pull the plugs and inspect them for fowling or abnormal appearance (this will help pinpoint) the affected cylinder, inspect the plug gaps and cracks on the plug and before you pull them out - check for proper torque as an improperly torqued plug (loose) can allow compression to flow past the threads (Misfire)

It could be a long list of things that can generate the P0300 code, which the PCM cannot see the specific cylinder, or it is across all cylinders, this is where the EGR system, Fuel System, Fuel Injector Circuit control, Vacuum Leaks, MAP Sensor, PVC Issues, Intake Ducting Leaks, Temp and Pressure Sensors , etc tie in and it is a crap shoot on what the issue is without looking at Live Data.

Since you had water in #4 - Suspect possible bad COP Boot - corrosion on the end of the boot.
and or due to the angle #4 sits at, the boot may not be all the way connected to the plug tip.
It is a (BY FEEL) connection. (if you pay attention) to the sensitivity of your hand you can feel the (Click) when the boot engages the plug.

If you shotgun anything - Shotgun a Coil and Boot on this cylinder and this is only due to the fact that you had water in the well at some point. (this would be precautionary only)

 

[Roscoe_t]

I understand that cold GDI engine misfires that go away when the engine warms can be a sign of intake valve deposits.

 

[JHC14]

So, if I understand correctly, you replaced the plugs as precautionary with a noted presence of water infiltration into #4 plug well.
Truck was running rough after this - Was it running rough BEFORE this?

6-Weeks and 8,000 miles - Light comes on and scanned - showing P0300, with a noted runs rougher when cold vs operating temp
You have replaced the DPFE sensor - was there any noted difference in driving after replacement?

I would not waste the money - throwing parts at it.
As the unknown is - Is it related to the Plugs / Coils or EGR or another area of concern.

The truck needs a scanner hooked up to see which cylinder or cylinders are registering the misfire.
This can be done with something other than a Code Reader; you need to view Live Data / Freeze Frame Data & Mode 6 Data.

There are a number of Live Data - PIDs to look at, Fuel Trims, EGR PIDs, O2 Sensor, Fuel Pressure, Map and Misfire Counter along with the Knock Sensor
another thing that can be done is pull the plugs and inspect them for fowling or abnormal appearance (this will help pinpoint) the affected cylinder, inspect the plug gaps and cracks on the plug and before you pull them out - check for proper torque as an improperly torqued plug (loose) can allow compression to flow past the threads (Misfire)

It could be a long list of things that can generate the P0300 code, which the PCM cannot see the specific cylinder, or it is across all cylinders, this is where the EGR system, Fuel System, Fuel Injector Circuit control, Vacuum Leaks, MAP Sensor, PVC Issues, Intake Ducting Leaks, Temp and Pressure Sensors , etc tie in and it is a crap shoot on what the issue is without looking at Live Data.

Since you had water in #4 - Suspect possible bad COP Boot - corrosion on the end of the boot.
and or due to the angle #4 sits at, the boot may not be all the way connected to the plug tip.
It is a (BY FEEL) connection. (if you pay attention) to the sensitivity of your hand you can feel the (Click) when the boot engages the plug.

If you shotgun anything - Shotgun a Coil and Boot on this cylinder and this is only due to the fact that you had water in the well at some point. (this would be precautionary only)

Wow...Thanks for all the great info. You sound just like my son. He is a mechanic in the AF.
I appreciate the through answer. I have one question, and I am not being a jerk here, but to hook up to a diagnostic machine and get these answers, wouldn't it cost more than replacing the coil packs and determining if this was the issue?
I would really like to hook it up to a machine and get these answers, but the dealers or a mechanic are the only ones with this type of hardware. Unless, I am missing something. You mentioned Live Date. Is that a program I can run on my computer or is it just live data while the truck is running?
Honestly, I know enough to be dangerous and that's about it.
I have run Forscan on it in the past and tweaked the lights and such. Enabled Babie mode and messed in radio screen start up sequence.
When I swapped the plugs I felt the "click" when reinstalled coils. I did not torque the plugs when I installed the new ones. I simply did them as tight as I have been for the past 50 years when I replaced plugs. I don't own a torque wrench, just a good ol Craftsman set I have had for 30 yrs.

I can definitely see how #4 could be the culprit. This is my most logical starting point.

thanks again for the plethora of ideas and possibilities. If the coil and plug are not the issue, then I guess I do have to take it to be scanned.

 

[airline tech]

Ok, you have Forscan, I suggest you search youtube on using Forscan to set it up for Live Data monitoring. It's not hard but with Forscan you have to know general (PIDs) and what they are.

It is hard to explain and cumbersome to get set up vs a Scan Tool, that's why I do not use Forscan for any Live Data monitoring - with a scanner all you do is click Live Data and every parameter PID is available to view.
With Forscan you have to select every PID over to the (Viewing) side of the table and you have to know the simple acronym in Forscan to know what it is.

Here are some examples of Live Data - It is a Live view of the various engine parameters, valve position, pressures, voltages etc.

My Autel Scanner - For the DPFE

Snap -On -Scan Tool (I Think)

Forscan: Fuel Trims and Other PIDS

My Autel - Blend Door Actuators

 

[airline tech]

I am just being logical - throwing 4 Coils at it, May or May Not fix the issue @ $68.00 Ea x 4
If that does not fix the issue, then they were replaced for nothing.
But then again - if it does cure the issue, you still do not know if any money was wasted as some of them might still be good.
Granted a P0300 Code can be very difficult to diagnose as it does not pinpoint down a specific avenue to go down, this is why Live Data is important and looking for a PID that appears out of spec to help in determining the issue.

Thats why I was asking was it running rough prior to replacing the plugs or did it start just after plug replacement?

If just after plug replacement - then I would possibly replace all plugs again along with #4 Coil & Boot as it is possible for a plug to be defective and or cracked.
If this is the case - this would be the minimum of shot-gunning parts, at the very least pull the plugs out and inspect them.
As this would be a highly possible cause, due to the fact that just after plug replacement - it ran rough and finally coded 6-weeks later once the misfire monitor picked up a high number of misfires at (highway speeds)
Whatever it is - by your description it is a gentle subtle misfire which may indicate an Improperly Gapped Plug

Another area to check - since you replaced the DPFE sensor, is the DPFE sensor itself and the attaching hoses. If the sensor is leaking or the attaching hoses this will create a vacuum leak - thus misfire. Was this replaced as a unit (with hoses) or the sensor and then re-used the OE hoses with worm clamps?
If using the OE hoses - suspect worm clamp not tight enough and leaking.

Again, this is where Live Data will help - the DPFE sensor and MAPT sensor readings will show DPFE askew and the MAPT sensor will show improper PSI under a load and the EGR opening percentage will not be correct.

 

[Dgc333]

P0300 is a multiple cylinder misfire code, if the misfire was limited to one cylinder you should get a cylinder specific code (P0301, P0302, P0303, P0304). I would be looking for a vacuum leak or a fuel delivery issue.

 

[airline tech]

P0300 is a multiple cylinder misfire code, if the misfire was limited to one cylinder you should get a cylinder specific code (P0301, P0302, P0303, P0304). I would be looking for a vacuum leak or a fuel delivery issue.

True - but sometimes the misfire can bleed over to 2 cylinders, this is the primary reason to view Live Data, to actually see what is happening.

 

[Dgc333]

True - but sometimes the misfire can bleed over to 2 cylinders, this is the primary reason to view Live Data, to actually see what is happening.

I agree 100% on looking at live data. BUT, if you had 2 cylinders misfiring then you would have two cylinder specific misfire codes.

 

[RangerBill]

Here is a quote from the Ford 2019 MY OBD System Operation manual on P0300 misfire detection code:
"If misfire is detected but cannot be attributed to a specific cylinder, a P0300 is stored. This may occur on some vehicles at higher engine speeds, for example, above 3,500 rpm."
https://www.fordservicecontent.com/ford_content/catalog/motorcraft/OBDSM1900.pdf

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