Well i have been having an issue for a little bit, the truck has been starting to misfire while in boost. sometimes it is fine and sometimes it is horrible. I was logging it today and the log showed something rather odd, the RPM jumped like 2k in 2 frames, look at the pic below.

I have swapped out the plugs and they are gapped at .030, i have tried .035 and the issue was the same. I did an ohm test on the coils and they appeared fine. I am wondering if the crank sensor is dying or screwed up.


Thoughts?

 

Are u on sd tune?

 

I would check the air gap for the crank sensor. I believe it should be around .020. Do you know what year the crank is in the engine? I believe the earlier ones came with the reluctor rings touching each other at the teeth where the later ones have a gap between the teeth. Not sure if that is your problem, but supposedly they changed it to eliminate a misfire condition (from my understanding)

What boost are you running? You might want to tighten up the gap a bit as you could be blowing the spark out.

 

yep SD tune. EFI Live COS3 in semi-closed loop.

I am running 8-10psi but now i can't go over ~5psi with it cutting out like that.

My motor is a 05 LQ9, how do i measure the air gap?

 

You gap it the same as you would a spark plug but instead of spreading the gap with the indicator you would adjust it by backing it out of the hole. What plugs are you using also and is it one cylinder missing or seems to be multiple?

 

I understand that part, but do i drop the pan to do it or what?

 

Is it actually misfiring, as in can you feel when it happens?

 

I'm sure you checked this but will ask. Have you checked the spark wires? Have you changed the burst knock in eflive for boost?

 

i guess it is a misfire or a sputter or it cutting out, whatever you want to call it. The logs look decent except for the spike. It seems to be getting progressively worse... Also i don't think it does it first drive of the day, but on the way home it really sputters/misfires/etc... never back fires or any KR... rather odd... Also seems to be down on power some...

 

The plug wires are new 10mm Taylors, i might try putting back the stockers...