Reoccuring Misfire Code?

Gamester · Jul 28, 2017

Hey guys,

So I keep getting on and off occasionally a thrown misfire code on cylinder 8. However, I never feel or hear any misfires and the code usually clears itself, but it didn't clear when it happened today, had to clear it manually.

Anyone having this happen? I'm thinking there is actually not any real issues going on, but not sure why the code comes up every week or so. I know what a misfire feels and sounds like, but haven't felt or heard any on this truck...

charonblk07 · Jul 28, 2017

Are you running oem pushrods or forged ones? I had a phantom miss at higher rpms, replaced plugs, coils, injectors, springs and it would get better but only increase the rpm that it came in. I just swapped out the oem pushrods for a set of Manley forged ones. My oem ones were still perfectly straight but with the higher lift of the cam and resistance from the increased cylinder pressure the rods were flexing in the head under repeated cycling.

Rupert · Jul 28, 2017

swap you #8 coil with # 6 ( or another that is easier to get to) and see if the misfire continues at #8, moves to #6 or goes away. check your conections for tightness cleanliness as you go.

If it moves to # 6 replace the coil.

If it stays at # 8 replace both spark plugs and start looking for chaffing etc. in the wiring leading to the coil.

If the misfire goes away...wait awhile it will come back.

Rupert · Jul 28, 2017

just saw you have a blower....I'm sure you have different plugs right?

HammerHead · Jul 28, 2017

I had a random backfire but the opposite you have. No code but it would backfire really loud. I went over the engine and never found the reason.

WilliamS · Jul 28, 2017

I have a phantom 7 misfire from time to time. It will ding at me a few start ups on random days are random temps. It will clear by time I get to work, then months will go by without a code. No rhyme or reason.

Gamester · Jul 31, 2017

Good suggestions, yea all the engine internals and electronics are OEM, might try the coil swap idea to see if that can narrow anything down. Thanks guys.

charonblk07 · Jul 31, 2017

Just curious, what plugs are you running right now?

Gamester · Jul 31, 2017

charonblk07 said:
Just curious, what plugs are you running right now?

Whatever came from the factory...

Rupert · Aug 1, 2017

Suggest you contact your blower boost cooler OEM and ask them for suggestion for spark plugs compatible with their equipment on your motor.

A different heat range/ different gap is probably needed, and will compliment your build.

charonblk07 · Aug 1, 2017

Gamester said:
Whatever came from the factory...

That's a problem then. Swap out to colder plugs for boost, I'd start with the Denso 3381s as they're 1.5-2 steps colder but are a projected tip. I ran them just fine on the D1SC and changed them every 15,000kms because I'm **** like that. Gap them at .030" and see how things go from there.

Gamester · Aug 1, 2017

charonblk07 said:
That's a problem then. Swap out to colder plugs for boost, I'd start with the Denso 3381s as they're 1.5-2 steps colder but are a projected tip. I ran them just fine on the D1SC and changed them every 15,000kms because I'm **** like that. Gap them at .030" and see how things go from there.

Ah, ok. I didn't think about that. I'll try that then, thanks!

charonblk07 · Aug 1, 2017

HammerHead said:
I had a random backfire but the opposite you have. No code but it would backfire really loud. I went over the engine and never found the reason.

Was it a backfire or lean popping? I find that when I come off the throttle from WOT there's sometimes too much fuel going into the exhaust and it's still combusting in the header. We tweaked the AFR to lean it out a bit and now I get lean popping in the exhaust which is perfectly acceptable with the additional air in a supercharger.

Gamester · Oct 27, 2017

Hmm, still getting misfire codes even on the newer colder plug, 3381s, any other suggestions on why I'm getting these "ghost codes" pop-up when I've never feel or heard any actual misfires from this truck?

charonblk07 · Oct 27, 2017

False knock is possible from a couple of sources like if you're running Stage8's locking clips or a hard line is against something and transmitting through the block. Your cylinder fueling could be unequal from mismatched injectors or your pushrods could be flexing at the higher loading frequency, can't remember if they were oem or forged ones. Were your knock sensors desensitized in the tune?

Gamester · Oct 27, 2017

charonblk07 said:
False knock is possible from a couple of sources like if you're running Stage8's locking clips or a hard line is against something and transmitting through the block. Your cylinder fueling could be unequal from mismatched injectors or your pushrods could be flexing at the higher loading frequency, can't remember if they were oem or forged ones. Were your knock sensors desensitized in the tune?

Wow, didn't realize that all that could be picked up by sensors enough to actually throw codes. I don't think we changed anything in the tune related to knock sensors, but that is a good idea to look into that and all the internals are stock on my engine.

What exactly would need to be done to desensitize the knock settings is there some threshold setting for this in HPtuner or something? If so, what number or percentage should it be set to for a supercharged stock internals engine like mine?

charonblk07 · Oct 27, 2017

Gamester said:
Wow, didn't realize that all that could be picked up by sensors enough to actually throw codes. I don't think we changed anything in the tune related to knock sensors, but that is a good idea to look into that and all the internals are stock on my engine.

What exactly would need to be done to desensitize the knock settings is there some threshold setting for this in HPtuner or something? If so, what number or percentage should it be set to for a supercharged stock internals engine like mine?

There’s a PID in the engine tab for knock sensitivity. IIRC it’s just a 0-5V signal so you can calculate how much you want to reduce it by a percentage. I’m up at work for another week so I can’t look at it to tell you for sure. I believe we had mine reduced by 50% with the D1SC but it’s completely dependent on your engine and how comfortable you are with the tune. If you’re pulling plugs regularly to check out their heat exposure you’re safer to run lower sensor sensitivity. As I told someone else earlier today, I don’t like disabling them because that’s the same as closing the bedroom door and going back to bed with the house on fire, problem’s still there you just can’t see it.

I would also think about a set of forged pushrods with an .080” wall. They’re good to have anyways with boost and it would eliminate one factor for sure.

Sent from my iPhone using Tapatalk

Gamester · Oct 27, 2017

Cool, we'll take a look at that on my next shop visit. Thanks

Reoccuring Misfire Code?

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