P0300 issues after IMRC lockout.

[Mankind]

I am having issues with my 2017 GT and would like to know if anyone else has seen this or may know what I am missing. Did a few searches a few different ways on the site and didn't see anything to help me.

Long winded background: Up until a month ago I was running all stock except the Exhaust. One day I had a miss and read two codes, P0308 and P0306. It was due new plugs so I stopped and picked up a set of Motorcraft. Installed all 8 and swapped the coils from driver to passenger to see if the miss followed. It did not, still had the miss and same codes. I knew there were issues with IMRC shafts so I went ahead and pulled my intake off. Sure enough, the right side shaft is broken. I Picked up a 2018 intake and lockouts, Roush CAI, and a tune. Cannot get rid of the P0300 that is now present. Data Logged for the Tuner and tried a few revisions, still a stutter and P0300 when I try to cruise at at consistent speed. Smoke test does not reveal any leaks, and all hose connections/caps are clamped. Me being a machinist I locked out the broken shaft and the left side shaft on the 2017 manifold then decided today to go back to stock manifold and air box with the tune, I still feel the stutter at cruise and get P0300. I even tried the stock tune to see if the P0300 will go away, no luck. Tried smoke test with current equipment on and still see no leaks.

Anyone else see the P0300 and feel the stutter when running a steady speed after their IMRC lockouts? If so, how did you fix it?

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[Supreme_5.0]

I am having issues with my 2017 GT and would like to know if anyone else has seen this or may know what I am missing. Did a few searches a few different ways on the site and didn't see anything to help me.

Long winded background: Up until a month ago I was running all stock except the Exhaust. One day I had a miss and read two codes, P0308 and P0306. It was due new plugs so I stopped and picked up a set of Motorcraft. Installed all 8 and swapped the coils from driver to passenger to see if the miss followed. It did not, still had the miss and same codes. I knew there were issues with IMRC shafts so I went ahead and pulled my intake off. Sure enough, the right side shaft is broken. I Picked up a 2018 intake and lockouts, Roush CAI, and a tune. Cannot get rid of the P0300 that is now present. Data Logged for the Tuner and tried a few revisions, still a stutter and P0300 when I try to cruise at at consistent speed. Smoke test does not reveal any leaks, and all hose connections/caps are clamped. Me being a machinist I locked out the broken shaft and the left side shaft on the 2017 manifold then decided today to go back to stock manifold and air box with the tune, I still feel the stutter at cruise and get P0300. I even tried the stock tune to see if the P0300 will go away, no luck. Tried smoke test with current equipment on and still see no leaks.

Anyone else see the P0300 and feel the stutter when running a steady speed after their IMRC lockouts? If so, how did you fix it?

I had a P0308 misfire code on a 2019 GT and it turned out to be a bad upstream O2 sensor on the drivers side. Replaced the O2 and the car has been running fine since and the code went away. Hope this helps.

 

[K4fxd]

Did you do a crank re-learn?

 

[Mankind]

Yes, and a Kam Reset.

 

[Black nasty]

I feel your pain...2015 gt pp 19,000 miles

2018 i. Imrc locked out
Headers
Jlt
Tune

Have a hard stumble at 3500 rpm p0305 p0300 code.
Tried compression and leak test.
New plugs
New injectors
Coil swap
Tune off and on

If I figure anything out ill let you know

 

[Cobra Jet]

Try the O2 as noted above, it's been posted in a few threads that a bad O2 can cause the very frustrating P0300... which is just a random misfire code not specific to any cylinder.

Check Crank sensor too - failure can be the sensor itself, the harness to it or the pins in the connector. If the crank sensor is failing, it also will throw various misfire P0300 DTCs. The only time the crank sensor will throw a specific crank DTC is if the sensor is disconnected or it has completely failed. Many have found even with a genetic misfire P0300, that the issue was related to the crank sensor. These sensors do not last forever due to their location and under hood heat cycles.
Check this thread:
https://www.mustang6g.com/forums/threads/misfire-at-high-rpm.174380/#post-3531453

AND this one:
https://www.mustang6g.com/forums/th...e-sensor-tone-ring.156234/page-2#post-3197692

VCT's will also throw a P0300.... plenty of threads on the VCT system.

i would start with the wiggle test making sure all wiring harness connectors in the engine bay and grounds are 100% secure. Then work from the least expensive repair possibility noted above. Don't do everything at once, you'll never figure out what the real issue was...

Approach it and diagnose 1 component at a time and don't just throw parts at it. The above are the most common possibilities, but that P0300 is not an easy one to diagnose.

---

Also I'll throw this below tech in for you in the event you have not seen it; it is tech about Ford's Misfire Strategy, it may help to also understand the code better.

This thread may give you some enlightenment to Ford's misfire strategies:
https://www.mustang6g.com/forums/threads/good-tech-article-on-ford’s-misfire-strategy.108076/

Also here is a pdf snip from the Ford Shop manual. which is "Coyote" specific. I'm including it because it gives a bigger picture of how to diagnose misfire events from the generic to the actual cylinder event codes:.
https://www.mustang6g.com/forums/attachments/hd-misfire-detection-pdf.538665/

 

[Mankind]

Thanks. I saw you post this in another thread and have already started going through ford’s process, sort of. CS is good, nothing on it and the plug was secure. I did some testing compared to a new one and they came out the same using my dvom so I put it back in and did a crank relearn. If Mother Nature would cooperate for one or two evenings I can go through everything pretty quickly but the rain is limiting my investigations, the bikes and the ’71 F100 resto project have the garage packed at the moment So I’m at her mercy. Going through and checking the plugs, coils, and plug gaps as a second guess of myself when the bottom fell out last night.

I will post findings, and lack there of, as I get the chance to poke and prod between rain drops In the evenings. This is my first Coyote hunt so I might be a lil noobish while doing it. So used to working on Dodges and LS motors this one got me having to do some research.

 

[Saleen0549]

Hello, I have a 2017 Mustang GT convertible Premium. Same P0300 code, found broken imrc shaft on the 2017 intake manifold. This would have been the third intake manifold. 48K miles on the car. All stock. Replaced with a new 2018 manifold, new plugs same P0300. Pulled the intake again and did the lock out. Same P0300 code. Any help would be greatly appreciated.
Thank you in advance.

 

[WildHorse]

Replace the 2 injector O-rings on each injector.

 

[Saleen0549]

Ok, i'll give it a shot. Thanks for the quick reply. Any brand you would recommend?

 

[WildHorse]

Ok, i'll give it a shot. Thanks for the quick reply. Any brand you would recommend?

OEM Ford.

 

[Saleen0549]

Thanks again.

 

[TopJimmyCooks]

Did that fix the issue?

 

[krazer]

I had a P0308 misfire code on a 2019 GT and it turned out to be a bad upstream O2 sensor on the drivers side. Replaced the O2 and the car has been running fine since and the code went away. Hope this helps.

Did you replace it with the OEM?

 

[Supreme_5.0]

Did you replace it with the OEM?

Yes, believe I ordered it off of AmericanMuscle.

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