Hopefully someone has experienced this before and can give some insight/knowledge. Car is an '06 LE5 turbocharged running E85. Have about 3k in the setup. Tune is finished and good.

First I'll say I started the car out on NGK LTR6IX-1 #6509 plugs, and they worked well gapped at .032". But would only last about 1k miles before the car would start knocking on very conservative spark timing (17*). I changed them to new plugs, same kind, and fixed the problem. After another 1k miles same thing started to happen.

After reading powell's spark plug suggestions and others experiences I bought NGK ILTR6A-8G and the car ran well on the .030" gap they came with. Then after about 4 pulls the car started to miss up top around 6-6.5k, I assumed spark blow out.

I brought down the gap to .024" but the car is still breaking up and losing power around 6500, still only on 9psi. I can hear it happening too, and it sounds just like the spark blowout did.

Could it be valve float? Or is it still spark blowout?

One of my buddies thought it might be a weak coil, anybody have this before? I haven't logged individual cylinder misfires so I guess if it is a bad coil I should be able to see the misfire just on a single cylinder. But did at one point get a misfire engine dtc when I stayed in it through the spark blowout.




CLIFFS: The car is breaking up around 6500 and only on about 9psi with NGK ILTR6A-8G at a gap of .024", could it be a bad coil?

Anybody got an extra coil laying around? And anyone know if an LNF coil would work? IDK if it's stronger or not tho.

 

I have kinda the same problem, but only when I did runs in the drag strip back to back,
Car will lose power and will misfire so much (by aeroforce interceptor) that the check engine light will blink couple times throwing the code of multiples misfire.
On rolling pulls it will almost never happen. Only happened to me at the strip and top of third gear, Joe (ItalianJoe) thought the same, valve float.

I have this happened with Autolite XP5263 and NGK LTR6IX-11 all gapped to .033"-.035"
Car have not been logged when this happens. And car is tune at 9-10psi.

Idk if Joe can pass by and give some info.

 

How old are your coils? I wouldnt immediately jump to spark blowout on 9psi, and 6500rpm is still well within the limits of the stock valvetrain (which is probably good up to around 7200rpm). You say that you start getting knock after about 1000 miles on a set of plugs, what do the plugs look like when you pull them? How does the heat range look? (discoloring on the threads, should only be 1/3 of the way up) How do the timing marks look on the ground strap? How is your VVT tuned for turbo? Responds correctly I suppose with the adjustments made for the turbo? Not too much overlap above 6k?

 

If Ur on e85 put the stock plugs back in no reason to run anything else

 

Yes!

Valve float shouldnt happen. S/C ive had 15 psi without issues.

 

Coils have 70k, and you can't just generalize by engine speed with boost because there is more force holding the valve open from the pressurized air.

Tune and vvt settings are good. Should never have overlap with a boosted motor, no matter the speed.

Cooler plugs won't make a high temp concentration at the strap and cause knock that way, I can try stock plugs but I don't think that's the reason.



I will try other plugs with a tight gap and try data logging the misfires, hopefully they're all on one cylinder and it's just a weak coil.

 

I never said a cooler plug. U Proly want a hoter plug on e85. But i found that stock ones work fine.
I have a lsj with a 2.5 pulley on a M62 e85 all that good stuff and the only plug i find to work well is a stock heat range plug.

 

Yeah I know, I meant I think I should be using a cooler plug because of the E and boost, but I'll give the stock plugs a shot.

 

yeah try a stock heat range.