Check Engine Light

[Nuzzman]

Hello,I was wondering if anyone had information relating to my issue.I have a 2017 Mustang GT Premium and several months ago my check engine light came on and the code was A P0300,I brought it to the dealer and they said I have some fouled spark plugs and it would be $600 to change the plugs but I said that was way too much money but they never told me what caused the problem.I replaced the spark plugs as well as the coil packs and it runs rough at times and smooth at other times as it seems to be random.After about 1,300 miles the check engine light came back on.A question I have is when it runs smooth does it delete the information in the computer causing it to go over a thousand miles before the light comes on again.Thanks in advance.

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[ORRadtech]

Your question is not easy to answer with a yes or no.
A misfire code should not clear on its own. The MIL may, or may not, go out but the code will be stored in the ECM. If the MIL is flashing it indicates an active problem that could harm the engine. Also, a MIL may, or may not, be for the same thing as before. Fouled spark plugs can be from a number of reasons. Fuel, oil, coolant are the big three. And any of those, if the cause is not corrected, can damage the catalytic converters and/or the O2 sensors.
I suggest you have the codes read and proceed from there.

 

[Nuzzman]

Your question is not easy to answer with a yes or no.
A misfire code should not clear on its own. The MIL may, or may not, go out but the code will be stored in the ECM. If the MIL is flashing it indicates an active problem that could harm the engine. Also, a MIL may, or may not, be for the same thing as before. Fouled spark plugs can be from a number of reasons. Fuel, oil, coolant are the big three. And any of those, if the cause is not corrected, can damage the catalytic converters and/or the O2 sensors.
I suggest you have the codes read and proceed from there.

Thank you for the reply,you did answer the question as to whether the information is stored in the ECM when it does run smooth it still does store it.Thanks again.

 

[Garfy]

Thank you for the reply,you did answer the question as to whether the information is stored in the ECM when it does run smooth it still does store it.Thanks again.

Yes, anytime the MIL goes on and later goes off on it's own, the DTC is stored in memory (unless someone clears it with a scanner or disconnects the battery). If the MIL flashes approximately once per second, it's an indication that the misfire can cause catalytic converter damage (of course if it's a malfunctioning injector that's not supplying fuel then there won't be cat damage as you won't have unburned gasoline going down the exhaust.) BTW, if you didn't replace the coils with OEM that could be suspect if the new coils fixed some issues but now has random misfire. I had an issue once with Oreilly coils that were made in China and they developed a random misfire mostly at idle in drive. Replaced them with OEM Honda coils and no more issues.

 

[Nuzzman]

Yes, anytime the MIL goes on and later goes off on it's own, the DTC is stored in memory (unless someone clears it with a scanner or disconnects the battery). If the MIL flashes approximately once per second, it's an indication that the misfire can cause catalytic converter damage (of course if it's a malfunctioning injector that's not supplying fuel then there won't be cat damage as you won't have unburned gasoline going down the exhaust.) BTW, if you didn't replace the coils with OEM that could be suspect if the new coils fixed some issues but now has random misfire. I had an issue once with Oreilly coils that were made in China and they developed a random misfire mostly at idle in drive. Replaced them with OEM Honda coils and no more issues.

Thank you for the reply,and I did use Motorcraft coil packs.Someone has said that the dampers on the runners could be malfunctioning causing improper air/fuel ratio.

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