Low RPM Misfire - P0300 or P0308 Codes? READ ME!

[Shifting_Gears]

Hopefully this will save time and a headache for those of you that get this problem.

I started experiencing a lower RPM misfire which was most prominent off of idle to 3k rpm. I would get an intermittent CEL which would produce a P0300 or P0308 code (random misfire or Cyl 8 misfire).

The misfire was constant until higher RPM and it smoothed out. The car had full power WOT but felt a little off down low.

Took it to the dealer and they confirmed my suspicions, it was a broken actuator rod on the intake manifold assembly. So one bank of IMRC’s was stuck closed and the other functioning. The entire assembly was replaced under warranty.

They ran an ignition, injector, fuel pump and compression tests all of which were fine. There are other threads about this occurring with the 15-17 cars. Not sure about 18+ but it seems to be picking up for the 15-17 models as age and mileage increase. My car is a ‘16 and this happened just short of 8k.

Hope this helps!

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[Nerass]

see.. i've got the same thing, but i have a cobra jet manifold so no IMRC's. fml

 

[Zelek]

Sounds like a great opportunity to get an 18 manifold installed!

 

[Sheenapple]

see.. i've got the same thing, but i have a cobra jet manifold so no IMRC's. fml

replace spark plugs, the impacted cylinders ignition coil, and the Purge Control Valve. other then that it may not be hardware related, but i don't have any experience with the CJ mani or IMRC lockouts

 

[Nerass]

purge control valve? like the evap?

i did coils, did plugs ( twice lol )

 

[Red65]

99% sure your intake IMRCs are cracked. Common issue with stock intakes on 15-17 cars if driven hard. Happened to mine a few months ago. Ford replaced it free of charge.

 

[Shifting_Gears]

99% sure your intake IMRCs are cracked. Common issue with stock intakes on 15-17 cars if driven hard. Happened to mine a few months ago. Ford replaced it free of charge.

Pretty much. The actuator rod snapped on one bank in my case.

 

[Motopopo80]

This happened to me recently after doing an CAI and Bama tune. I get P0300 and P0302 misfires at 3000 rpm. Its constant. Thought it was tune but datalog suggest otherwise. Looks like I will be returning to stock and taking it into Ford under warranty. 2016 21K miles.

 

[catchthecarp]

New intake being installed today, car had 24K on it before the actuator rod on one bank went tits up.

 

[Motopopo80]

New intake being installed today, car had 24K on it before the actuator rod on one bank went tits up.

Did this happen while you vehicle was Stock?

 

[catchthecarp]

Did this happen while you vehicle was Stock?

Yes, engine is stock other than an AFE air filter. It's a DD, last Monday I could feel it wasn't running right. The symptoms were similar to what others have described, sluggish at low RPM's with the occasional miss but ran OK at highway speeds. The car didn't throw a CEL until Thursday (P0308). CEL was off when I started it on Friday morning but lit back up on the way to work and stayed on after that. Dropped it off at the dealership yesterday and covered under warranty. The only downside was I had to rent a car. The dealership has loaners but you have to make a reservation and the next available date for a loaner was two weeks out. I ate the rental charges and got the car fixed.

 

[Motopopo80]

Yes, engine is stock other than an AFE air filter. It's a DD, last Monday I could feel it wasn't running right. The symptoms were similar to what others have described, sluggish at low RPM's with the occasional miss but ran OK at highway speeds. The car didn't throw a CEL until Thursday (P0308). CEL was off when I started it on Friday morning but lit back up on the way to work and stayed on after that. Dropped it off at the dealership yesterday and covered under warranty. The only downside was I had to rent a car. The dealership has loaners but you have to make a reservation and the next available date for a loaner was two weeks out. I ate the rental charges and got the car fixed.

I have a 2016 with 21k miles I purchased last month. I recently installed a C&L intake and Bama 91 octane tune. After two days I started getting P0300 and P0302 (Cylinder 2) misfire codes and CEL flash and steady on. This happeneds also at 3000 RPM and never at WOT. After two weeks of datalogging and having Bama refine tune, same issue. They said replace spark plugs or ignition packs. After reading several threads this seems like an issue. I will be putting stock air box and tune back on and hopefully issue can be taken care of on warranty. I can only hope the techs will listen to my suggestion the CMCV/ IMRC and not have me repeatedly come back to finally fix the real problem.

 

[Shifting_Gears]

The dealer will run diagnostics regardless as it’s their protocol to rule certain issues out. I would certainly mention to them what you suspect it is, as chances are that’s exactly the issue. They should be able to rule it out pretty quick versus throwing parts at it to see what fixes it.

For mine they scanned all the codes, ran a complete diagnostics test (testing fuel, spark, ECU) and also a relative compression test to ensure it wasn’t an internal issue. I told them before I turned the keys over it was an IMRC failure and they were receptive to it and told me I nailed it when they called me to inform me of their findings.

 

[catchthecarp]

Here's the mechanic's write up on my repair, checking IMRC valves was the third step of the diagnostic: Removed the spark plug from cylinder 8, inspect and check gap, within spec. Swapped coil pack to another cylinder and misfire did not follow. Per SSM(I have no idea what that is) remove intake and inspect IMRC valves for movement. Bank 2 IMRC valves not moving when actuators are moved by hand. Replaced intake manifold and lower injector O-rings. Cleared DTC and test drove.

 

[Motopopo80]

Here's the mechanic's write up on my repair, checking IMRC valves was the third step of the diagnostic: Removed the spark plug from cylinder 8, inspect and check gap, within spec. Swapped coil pack to another cylinder and misfire did not follow. Per SSM(I have no idea what that is) remove intake and inspect IMRC valves for movement. Bank 2 IMRC valves not moving when actuators are moved by hand. Replaced intake manifold and lower injector O-rings. Cleared DTC and test drove.

As of yesterday, the manifold was replaced under warranty and all is good. No codes at 3000 rpm.

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