Id like to quickly note that ive done all the searching humanly possible..and that YES , we've already done the po300 fix, and the code does not come up anymore We have also replaced all the main things that usually come up, ie : spark plugs, coils, tunes, bov, po300 code, boost leak tests,all good or replaced new, etc etc

The problem happens when i go into full boost at WOT. The car misfires hard and continues randomly misfiring throughout the powerband.\

We've tried replaced the spark plugs ( bpr8es, and bpr7es , at every gap from .26 to .19 even) , Replacing the all the coils with new ones, adjusting the tune, etc etc

My mods are:
Forced Performance Fully Ported Green Turbo
AMS Front Mount Intercooler
Full Race Prostock Exhaust Manifold
HKS Hi-Power Exhaust
Brian Crower 272/272 Cams
Injen Hardpiping Kit
Injen Intake
Hallman Manual Boost Controller
Tanabe Downpipe and Test Pipe
stock ecu custom Tuned (the tune is fine)
Exedy Twin Carbon/Carbon Clutch
Fidanza Lightened Flywheel
Misihimoto Evo 7 Race Radiator
Optima Red-Top Battery

Running on e-85 and pte 1000cc injectors. We were having the same problems on pump AND race fuel btw, and also ran meth with both.

Ive researched about possible ground issues, but am not to sure about that. The misfires are even happening at close to stock boost pressures (21psi) although it randomly goes away after the car has been running for a while...(not a warming up the car issue, car is properly let warm up) so it's not like im producing crazy amounts of power or anything. Logs show No knock, and my air fuels are perfect besides when the car misfires and they fluctuate during the misfire.

At first, I was getting all that 5th gear problems and found out about the po300 code and got that part resolved but we are still have misfire issues all around. The only codes that come up now are for the o2 sensors... i usually just clear the code since i run a straight pipe with no cats but have started thinking of replacing these too.

this is driving me insane. it's a waste of time trying to get the car tuned and dialed in with these misfires...and the problem seems to jump around regardless what tune or how much boost we run...it just revolves around the damn misfiring.

Sorry for the long read but Im begging for any relevant advice on this problem.

Also Ive done two full boost leakdown test and there are no leaks. I have also switched back to a stock evo 9 mr bov.. I had an aps twin vent but we removed it just to make sure that wasnt the problem.

Everything seems to point toward ignition, but there is absolutely no reason why the ignition with new coils and new spark plugs shouldn't be able to handle a measly 21psi on an fp green.

Im almost to the point where i just want to sell the car because there is no reason why it should be doing this! everything seems great except for when the car starts to randomly misfire under wot loads....Logs show everything is great besides the up and downs cause of misfires. Just everytime i try to got WOT it starts misfiring.... thanks for reading. any help would be appreciated.

 

fuel pressure? injectors pulsing? tps adjusted properly? any cooling issues? ect? i've seen all these provide some of the issues you are having. a weak f pump may work fine at low loads, but may not pump as hard at wot. the rear o2 sensor helps the computer determine your a/f ratio, so that may also be affecting it. if the rear o2 senses too much fuel out the back,(which is possible, cause you have no cat, ) it may tell the comp. to compensate by going lean and wigging out the comp. it may still be the tune too. you either need to diagnose it or take it to someone who can. throwing parts will just get expensive. good luck.

 

which plug wires?

 

i had same issues i found oem plug wires work best.... also everything heavens turbo said

 

o2 gapper for the rear sensor, oem iridium plugs specific for your 8 or 9 (dont gap them) and you should be good to go.

 

How does your plugs look? Do you have a log or graph showing what it does when misfiring?
Does the car jerk or just lose power?

 

it's a new radiator so no cooling issues...in fact cooling is better now. Im not sure on the fuel pressure but when not misifiring the air/fuels are perfect. so I didnt think it was fuel pump....i am worried about the o2 sensors and have been looking to buy some replacments...

It's not the tune. My tuner is one of the best on these boards, and he's actually the one stopping me from buying tons of parts i dont need...thanks for the great advice though. it's def. stuff ive been thinking about.

 

stock coils and wires..but replaced with new oem ones. well the coils are new, but i check all the actual wires for corrosion ,wear etc etc

 

o2 gapper has already been applied. quite sure the rear o2 is going out or is already out. oem iridiums already tried , still bad. thanks for help though

 

my plugs look like ther are misfiring pretty much...they should looks nice and clean with the e though....we have does tons of logs and graphs...but the only thing they show is up and downs in the calc loads when the car mis-fires. there is no knock, no bad air fuels , nothing....seems normal but inside the car the misfiring is obvious . No jerking or loss of power except for the instance of the misfire....it's just a hell of a lot of popping starting with the initial one at first thats big, then the others...

 

I've had misfiring issues, never like this so I'm going to throw some ideas out there that may or may not help you and your tuner figure it out.

So it's only at WOT specifically?
Is it in any gear?
Would putting in a boost controller and turning down the boost to say 12 PSI help isolate the issue?

I had the CEL's even with the spacer and ended up having to get one of these which resolved my rear o2 sensor CEL - http://www.o2simulator.com/index.php...5a85894f4a1299

What happens if you go gradual throttle to say 95% and hit the 21 PSI, does it run ok without breaking up?

 

we have a boost controller and have been moving it around to see if it helps, it doesnt. It's in every gear after first and i dont do pulls in 5th....if i do a slow pull, it does it also just maybe not as much but it's still present. Ill look at that 02 simulator though, thanks for the help

 

try swapping out the battery.bad batteries can cause misfire issues.

 

really? ive never heard that. interesting! thanks

 

So was it the battery then?