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CEL Won’t GO AWAY! HELP!

TheNetcode

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Hey guys,

I own a 2019 Mustang GT (manual) base with the following mods:

JLT CAI
Oil Catch Can
X-pipe/Resonator Delete
VMP E-85 Tune

I have had this CEL on my dash for about a month now and nothing I do seems to make it go away. I ran my SCT tuner device and I got codes P0300, P0301, P05A1. I’ve changed out my spark plugs, changed out the coil pack in cylinder 1, replaced the 02 sensors, cleaned the MAF sensor….but It just keeps coming back. Can a bad grille shutter sensor cause codes P0300 and P0301 or can it possibly be a bad purge valve? The car has only 31k miles on it.

Any thoughts?
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KingKona

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Cracked intake manifold.
 

KingKona

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While kona is known to talk shit I'd agree with that being a possibility. And yes seems fairly common on the coyotes. It shouldn't affect the active shudders though so you may have multiple issues going on. I wouldn't think the active shudders would cause a misfire code either.
 

SheepDog

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Hey guys,

I own a 2019 Mustang GT (manual) base with the following mods:

JLT CAI
Oil Catch Can
X-pipe/Resonator Delete
VMP E-85 Tune

I have had this CEL on my dash for about a month now and nothing I do seems to make it go away. I ran my SCT tuner device and I got codes P0300, P0301, P05A1. I’ve changed out my spark plugs, changed out the coil pack in cylinder 1, replaced the 02 sensors, cleaned the MAF sensor….but It just keeps coming back. Can a bad grille shutter sensor cause codes P0300 and P0301 or can it possibly be a bad purge valve? The car has only 31k miles on it.

Any thoughts?
Check the IMRC operation on the passenger side bank. You will need to remove the intake manifold, but it isn't that difficult. The plastic shaft breaks. This was more common on Gen2 intake manifolds, but may be something to look at. How long have you had the VMP E85 tune on it?
 
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TheNetcode

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Check the IMRC operation on the passenger side bank. You will need to remove the intake manifold, but it isn't that difficult. The plastic shaft breaks. This was more common on Gen2 intake manifolds, but may be something to look at. How long have you had the VMP E85 tune on it?
I’ve had the tune for about a year now with no issues, but the CEL appeared about a month ago.
 

SheepDog

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I’ve had the tune for about a year now with no issues, but the CEL appeared about a month ago.
When you clear the codes. do they come back immediately or does it take a while? Do you notice any surging, bucking, driveability issues?
 
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TheNetcode

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When you clear the codes. do they come back immediately or does it take a while? Do you notice any surging, bucking, driveability issues?
No surging or buckling issues. Honestly if the code wasn’t there…I wouldn’t think anything is wrong with the car. It’s running just fine. I clear the code and it usually comes back the same day or the following day.
 

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junits15

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Just for sanity's sake, have you tried flashing back to an e10 gasoline tune to see if the problem exists there?

That would help you narrow down if this is a hardware failure or not. I'm guessing its a hardware failure, however e85 is notoriously hard to ignite especially at full concentration. If you've swapped plugs it would point to some kind of electrical fault potentially.

The crank position sensor and tone ring are used to detect misfires, might be worth at least putting eyes on that connection it to see if it's ok. Could also be coil packs, through unlikely. The fact that its all on Cyl 1 is some kind of clue but not sure what it could mean.

I'm doubtful that the grill shutter thing is related, however the AGS (from what I remember the last time I saw the wiring diagram) does have a data bus going to it. Which may cause issues if the terminals corrode and make a connection. Might be worth checking that too.
 

SheepDog

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No surging or buckling issues. Honestly if the code wasn’t there…I wouldn’t think anything is wrong with the car. It’s running just fine. I clear the code and it usually comes back the same day or the following day.
All 3 codes come back at the same time?

I wouldn't think the shutter code has anything to do with the misfires. Look inside the grill and make sure something isn't stuck in the shutters. The motor that opens/closes them can fail.

For the misfire, aside from the tune being a possible issue, you can try moving the injector from Cyl 1 to Cyl 2, but again, I'd be pulling the intake manifold off to makse sure the IMRC valve shaft isn't broken.
 
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TheNetcode

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Sound like your tune
Well the tune has been working flawlessly for about a year with no chance, so it’s hard to believe it’s the tune all of a sudden.
 

BlackandBlue

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Go back to stock first.

You have a problem that showed up after changes were made. The only way to know if they are related is to undo the changes.

It could be cracked pistons or it could be a small leak on MAF sensor and everything in between. Go back to stock and reassess.
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