P0300 woes


blakbearddelite

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I've been getting the P0300 (random, multiple misfire detected) on the Mustang in the last few months. Nothing has changed on my set-up. Kenne Bell @ 10psi, BAP, and a KB tune installed by Tim Barth.

Any other recommendations on what to look at?

Plugs, ignition wires, coils, vacuum leaks, EGR.

I'm hoping it's not any of the mechanical engine problems like valve problems, leaky head gaskets, or low compression.
 

Yaj Yak

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whats yer gap at
 
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blakbearddelite

blakbearddelite

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I'd have to pull a plug and see. Do plugs need to be re-gapped as maintenance? I mean, the kit was put on the car in 2017 with new plugs. And I didn't start getting the P0300 until a month or so ago.
 

Yaj Yak

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I'd have to pull a plug and see. Do plugs need to be re-gapped as maintenance? I mean, the kit was put on the car in 2017 with new plugs. And I didn't start getting the P0300 until a month or so ago.
no, not as regular maintenance

my boss's whipple 5.0 f150 i had a hand in putting together, was together for quite some time then started getting the p0300 code, when i talked to whipple they wanted me to check the gap.

it can blow the spark out if they are gapped to big.

it should have NGK LTR7IX spark plugs, gapped to .028”
i checked the gap and they were .033", i tightened the gap on all plugs and code/blowout never returned.
 
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blakbearddelite

blakbearddelite

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Ah, gotcha. That's probably the easiest thing to start with.
 

ZXMustang

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If you are running the TR6 plugs, I'd swap them for the NGK BR7EF. Kurgan of all people recommended them to me for my last boosted mustang and they worked well after I was having problems with the TR6's. The non projected tip stops spark blow out from boost. It would be where I would start.

https://www.summitracing.com/parts/ngk-3177?rrec=true
 

Mr_Roboto

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35 seems really wide at face value and seems like a good spot to start.
 

CMNTMXR57

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.035 isn't wide that wide for a blower motor. The Caddy's supercharged LC3 is .040.

Also, do you have a modular coil setup? They usually use a spring like connector to mate to the plug tip and sometimes they fail. Might see if swapping the coils pack (if you can identify which cylinder is doing it in a history menu), and see if it moves with the coil.
 

1quick

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I run .027 gap and the ngk 6510’s are where it’s at for the blower coyotes, I change them every season, seems like they start to develop a miss after a while on 93 so I just started changing them every year
 

Tight Lines

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I wish you luck figuring it out. I have been dealing with the same code for over a year. I have changed plugs at least 3 times. I went through a stretch where i would get the code after the second start up. Currently I actually opened the gap slightly, cleaned my MAF sensor and I also found that I over tightened my CAI tube and slightly deformed the bottom of it. I took a heat gun to it and reformed it back to its original shape. With fixing those three things, I am currently about 200 miles and some hard driving within those miles and the code hasn’t come back. I’m not saying I fixed it but hoping I did.
I have read a crank relearn can also help with the code. Gear changes and clutch changes should require the relearn to be done. You can do it with your SCT device.
Have you touched your crank pulley at all? If so, make sure the bolt is tight.

Again, good luck, I think I have truly lost hair over this f&$king code.
 

Jeffs FRC

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The P0300 code is pretty common on Coyotes and is usually cured by a crank relearn or KAM reset or both. I would start by doing both of those procedures as they are extremely simple to do.

I've also heard some aftermarket clutches can be responsible for that code and the cure is a different clutch. Cant remember which clutch or clutches were claimed to be problematic...
 
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blakbearddelite

blakbearddelite

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I did do the crank re-learn after I had my clutch swapped in 2017. You think I should do it again?

Strangely enough, the P0300 code cleared itself yesterday and it hasn't come back yet today...with some hard pulls. Fuck if I know.
 

Jeffs FRC

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I did do the crank re-learn after I had my clutch swapped in 2017. You think I should do it again?

Strangely enough, the P0300 code cleared itself yesterday and it hasn't come back yet today...with some hard pulls. Fuck if I know.
If it comes back I would do both. It wont hurt anything, and most of the time it'll get rid of the P0300 problem.
 

CMNTMXR57

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It will clear after a certain consecutive successful operating cylces without another failure. The code will then get put in a history file and clear from there after a longer time without failure.

I know this is a f..., but GM P0300 misfires is 3 consecutive successful operating cycles to clear from the current DTC status (which illuminates the SES/CEL light), at which point it moves to a history DTC, and will be there until 40 consecutive successful operating cycles have happened.
 
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blakbearddelite

blakbearddelite

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Ha, thought of this meme when I turned the car on and the P0300 code was gone:

 

CMNTMXR57

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I've been waiting for the bulb behind the CEL on the old van to burn out. NFG's on it until now that I have to go pass the emissions test to re-register.
 

Ron Vogel

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I run .027 gap and the ngk 6510’s are where it’s at for the blower coyotes, I change them every season, seems like they start to develop a miss after a while on 93 so I just started changing them every year
On gapped plugs I’m at .020-22. But I’m probably running more boost than you are. Valve stem seals could also be a culprit
 

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