transaminator99

iTrader: (3)

Lq4 with a t7875 on 21psi
Btr dual springs and hardened push rods
3 bar with alky control 100% methanol
Br7ef gapped to .018 brand new plugs
Afr 11.3 to 11.5 wot
Heat sink coils with stock wires

Can't get rid of the blow out at high rpm (5900 or so) , thought about trying ngk 1049 (8 heat range) and new wires , just trying to see if there is anything else I'm overlooking , car runs great in any other condition , on 18 to 19psi it doesn't do it , did a log today and only thing abnormal was kr was pulling 1 to 2 degrees out when I was experiencing blow out .... any help is appreciated

Blown06

iTrader: (32)

are you on a 411 pcm or aftermarket efi system? Have you tried increasing the dwell?

transaminator99

iTrader: (3)

It's on a stock ecu in a 99 trans am , no I haven't messed with anything to do with the coils just swapped them in case the old ones were the problem since I had the truck coils laying around

hellbents10

iTrader: (10)

Run the dwell at 4.5ms and check exhaust back pressure too.

stevieturbo

Genuine coils or some sort of copies ?

No way should you be having spark problems at that level.

transaminator99

iTrader: (3)

They're genuine gm coils , I know it's driving me nuts , I did the ngk 1049s today and it still does it

transaminator99

iTrader: (3)

I'm gonna look into the back pressure but I'm not savvy with tuning so I wouldn't know where to begin with changing the dwell for the coils lol

gametech

iTrader: (1)

Do you trust that your valvesprings are OK? If not, it could be valve float instead of spark blowout.

transaminator99

iTrader: (3)

Yeah they only have a few thousand miles on them , they're btr duals but if I can't find anything else I'll pop the valve covers off and inspect

rotary1307cc

iTrader: (5)

Close it up more

foose04

iTrader: (4)

Wow, this sounds like the same damn thing I'm dealing with.

21-22psi, .018 gap on ngk 1049s. Even got the random knock he said. E85, 15.5-16.5 timing. 180 eng temps, and AITs below 120.

5.7L 9.5 compression S480/92 1.0 t4


I was wondering if it's 112k OEM truck coils are tired. Thinking about trying those 15% hotter Accel coils. Wish hey wasn't yellow, they ugggly.


How tight can you go?

stevieturbo

The chances of this being spark blowout is almost zero.

69-chvl

iTrader: (11)

Try a ground wire to each coil pack to a good ground point.

yenkomike

iTrader: (2)

are you running out of fuel pump. they can go from 11.0 to way to lean very fast if you run out of pump.

transaminator99

iTrader: (3)

I'm running a walbro 450 and a stock pump as my second pump , I have a brfpr and 60# injectors plus 100 percent methanol , the car made 780rwhp and 811rwtq and I can drown the motor with methanol if I turn it up lol so I don't think it's fuel , plus the afr is good every single time it does it , maybe it is something else but it stutters or sounds like fast gurgling at high rpms and it's not constant ,it'll go in and out really fast sometimes and sometimes it will do it worse .... I'm just out of ideas

neverstop

simple but worth checking all the grounds and making sure they're all immaculate. My car certainly runs better since I cleaned and redid all the grounds and my car has fairly lowmileage

ls3fox

How about taking a video so we can hear what it does

stevieturbo

Could be many things....surprised your tuned with all the info etc to hand doesnt have any suggestions ?

Could easily be far too rich...widebands dont always tell the truth

JoeNova

This same thing just started to happen to me after turning the boost back up to where it was last year. I changed to a TBSS intake/90mm TB over the winter and rebuilt the hotside to flow better (more gradual bends).

At 10 PSI I was fine. Even had to add 20% fuel over last year.

Now at 21-24 PSI, I get lots of what sounds like misfiring at 5000+ RPM.
I did change a couple of plug wires because I needed the longer ones I was using on another build, and went with a larger water/meth nozzle (I run 70% water/30% meth). I also added a brake booster. It seems like I might've either screwed up a ground wire somewhere or possibly picked up a boost leak since most of the cold side/intake has changed.

I run the same plugs as you with a much wider gap (.028) and didn't have this problem last year. Same coils, same AFR.

transaminator99

iTrader: (3)

I don't follow the first part , maybe I'm reading it wrong , but I'll throw another wideband in it and double check the afr