From what I know about reading plugs my plugs are too hot. These are ngk 8's.







Im having a misfiring/backfiring when I turn up the boost. It happens when I go wot, so I went wot (17-18psi) and as soon as it happened I shut down and pulled the plugs. At 12psi no problem. The plug heat range is the only thing I havnt changed yet trying to find the problem.

 

Oh and the afr are good 12 spool up and 11.6-11.9 after. Ive tryed richer afr, lower timing changed plugs, wires, coils, new battery, alternator tested good, injectors where just cleaned, timing is dead on, no boost leaks, compression is great across. And all the plugs look the exact same. Ive even tryed e85 and 93.

 

EVO VIII? What are the plugs gaped at?

 

What he said /\/\...gap them at .025" to start and see if that fixes it. If not try .022"

I run the iridium BPR8EIX and had to gap them at .025. From the box they are usually .028-030"

PS I run 25 psi tapering to 22 at 7000

 

Plug gap has no effect, Ive gone from .020 to .028. There .023 in the pics. Built 2.4l evo8

 

I'm curious, I'll subscribe.

 

define "misfiring/backfiring" for us please. video?

 

have u tried one step colder plugs?

 

bult 2.4......what cams & what cam timing?

fwiw, i am a fan of denso iw27's.

by swapping all the parts that you did, suggest that you need to look elsewhere....

so does it misfire rolling into it @ 5k & ~6500/7k???

did this problem just start happening or is it a new problem with the build or new parts??

 

Cams are -3.75*, to make them 0* for the taller deck height. It misfires as soon as it hits full boost at WOT no matter the rpm unless I turn the boost down to 12psi.

I was pushing 22psi on e85 before without any problems. Then I started getting this problem. after I got a full tank of gas, but I DD the car without goin into boost for 4days also. And it was still happening at 12psi. I found a spark plug wire that was rusty where it goes to the coil pack, I replaced the wires and its fine for 12psi. But If I try to run any more boost it missfires.


By misfire it almost sounds like a 2step.

 

and the backfiring is through the exhaust? Just for laughs I'd try a set of good old fashion cheap *** NGK BR7ES gaped at .022 worst that can happen is you waste $10.

 

my car did that once. it seemed as if the ignition was weak. turned out to be a leaking headgasket. water putting out the fire.

 

Compression is perfect I highly doubt its the head gasket. And the plugs are not wet.

 

Just tryed BPR9es plugs gapped to .024, slightly better. There was a noticeable differnce, but still there. Im gonna gap them to .020 which they came gapped at. And see if it helps more or not at all.

 

check your ignition wiring. I had loose wiring (earths etc) and it caused massive faults with spark. Clean your earthing points and retorque all your earth bolts and try again