Misfire, Check Engine Light, Goes away if I turn engine off then back on.

[Stinger-Performance]

I was merging into traffic yesterday and the car started misfiring. I got off the throttle and tried to just cruise and it was still misfiring. I pulled over, turned the ignition off, back on, and the problem went away so I drove easy (tried to keep it at low boost) the rest of the way to my destination and back home. I then tried a hard acceleration near home and logged the behavior (attached). I noticed AFR shows full lean at idle/cruise after it starts misfiring which doesn't tell me much other than confirming it's misfiring (incomplete combustion = high o2 reading).

The car's ran perfect with the JB4 for about 25k miles and I've changed nothing in that time so for this to show up out of the blue without any hint of misfire before is a bit odd. I'm familiar with misfires as I've owned a ton of turbo cars but I've never had one that doesn't clear up until turning it off/back on, and they typically only happen in boost, not under all conditions, so I'm a little confused by what could be happening.

Can someone look at this log file and see if anything in particular looks out of line? Thanks!

 

[General_Vodka]

about 25k miles

Um that's a long time to go without looking at your plugs and coils. Especially with a jb4. I would start there for sure.

 

[Stinger-Performance]

I'm running the upgraded plugs like they suggest with the JB4. I wasn't sure how much life people typically get out of plugs on these cars but that was something that crossed my mind as a possibility. The ability to fix the misfire by shutting the engine down for a second is what's throwing me off.

 

[Terry@BMS]

Misfires clear on restart.

Read the codes and see waht cylinder it is, and check that plug first. But at 25k miles likely time for plugs.

 

[General_Vodka]

I'm running the upgraded plugs like they suggest with the JB4. I wasn't sure how much life people typically get out of plugs on these cars but that was something that crossed my mind as a possibility. The ability to fix the misfire by shutting the engine down for a second is what's throwing me off.

HKS then I assume? Makes sense, if it wasn't HKS then your issues would have started much sooner.

 

[Stinger-Performance]

Thanks Terry. That's what's weird, when I check codes in the JB4 app, it says no codes present. This is always after I clear the misfire. I try to check for stored codes but I can't ever get it to do so.

Yes, they are HKS plugs.

 

[Nkcmetro]

I had my Denso plugs in for 22k then started the cyl 6 misfire. I pulled all the plugs, the electrodes had been burned almost all the way off. Plug gap had gone up to .055 on all 6. It seems like I read somewhere that the Denso's are good for 18k miles or so. Needless to say that a new set of plugs corrected my misfire.

 

[Stinger-Performance]

My problem resolved itself. I drove it nice for a couple weeks (actually my wife did, it's her daily driver) while I contemplated what plugs I was going to get and then when I tried to replicate the problem it ran perfect. I assume it must have been a bad tank of gas or something.