For starters here's my mods list:

Large Street Port with 1000 miles or so on the engine
Ported UIM
Bosch 044 Pump
CJ Motorsports Fuel Rails
750/1680 injectors
Turbonetics T-76
Tial 44mm Wastegate
MSD 6AL on leadings
Blaster SS coils on all plugs
#9 Plugs all around
Power FC
AEM Uego Wideband
Apex'i N1 Exhaust
Midpipe
Apex'i Hybrid Intercooler
Koyo Radiator


Now here's my problem:

As soon as I hit 5000 rpm, free reving or under load, I get serious breakup. It is especially noticable when free reving right at 5000. If i rev real slow the RPMs break up so much that they actually drop by 100 or so until there is enough throttle to bring it back up a little bit. Once over 7000 it breaks up less but it sounds almost like it is running on one rotor. I shut off my leading spark and it ran the same other than a slight RPM drop and the inablity to hold idle. Same thing when I unplugged my trailing plugs. The car hasn't run right since I put it back together and I've made this post before but no one has been able to help me. My AFR is between 10.5 and 11.4 during break up. The plugs are pretty much brand new, new spiral core wires as well. I'm really stuck at this point, please someone help me!

 

let me guess your running an s5 setup

 

Clean all of the grounds on the wiring harness (ie sandpaper) and see what happens.

 

i have the same problem on a '93 FD... at about 5k rpm leading ignition starts to break up
Trailing works fine at any condition.

tried nearly everything:
1: replaced spark plugs (ngk bur7eq > L, bur9eq > T)
2: replaced plug wires
3: replaced leading coils
4: replaced igniter
5: full rewire from ecu to igniter; from igniter to L coil (also b+)
6: brutal ground wire from battery to chassis, battery to engine
7: replaced semi corroded screws at igniter (grounding)
8: rewired fuel pump
9: replaced fuel pump (walbro)
10: checked fuel press
11: replaced fuel filter
12: replaced primary and secondary injectors
13: removed all emission parts
14: removed double throttle system
15: replaced stock ecu to apexi power fc
16: checked pri, sec injector wiring from ecu to injectors
17: checked map, tps, cas

still have the problem...

wbo2 readings below 5k rpm are ~12.5; at 5k rpm it drops to 10.3~11
imo rich mixture caused by incorrect burn because of ignition break

im gonna try:
1: replace pri injector o-rings (when i replaced injectors o-rings looked fine)
2: replace fuel rail
3: rewire cas (shielded wires)
4: ??? what else??

engine compression is in the specified range in all 6 chambers

 

FC right? remove the crank angle sensor and check for chipped teeth on it

 

i had this same problem after installing the okada plasma booster ignition...car started breaking up...uninstalled it and it still happened...tried different coils and stuff but nothing...i installed the hks twin power and it stopped the breakup...i know i didnt "fix" the problem but it seems to work well for now...

 

wow!..u did a lot of work!...i really hope you get things sorted out...its a really crappy feeling when u cant seem to get your car working well

 

Get rid of the MSCRAP boxes and put some crane boxes.

Are you running suppressed igniton leads?
Good chance the wiring going to your crank triggers is shot. Most likely at the plug too.
common problem.
Add earth strap from block to chassis, and chassis to block.

 

ima with him-
also -
power FC is trying to wastespark the leading ignition
- at 5000 rpm your MSD has dropped to single spark , yet is trying to still fire twice per chamber ( wastespark )
this brings a couple of scenarios

-at 5000 rpm, there isnt the required dwell period to saturate the coil used
= spark blow out
( aftermarket ECU's with full sequential ignition may avoid wastespark, or turn it off at certain threshold RPM's so as to maximaise high rev available time for saturation of the coil )

- blaster coils are known to have heat issues ( to point of explosive fail )
when used with long saturation periods, or if used at reduced primary resistance
( so they may be overheating and failing at those RPM's )


and MSD boxes / HEI ignitiers self limit current in overheat situations
( ie used with a coil of too low a primary resistance that is effectively on for large portions of every second at high rpm = likely your scenario )


whats needed to cure it? well, find out if its
- a self limit from current protection / overheat fail
- or if its simply a spark blow out
for the former , change coils, or add a resister to the primary windings power
and or alter dwell setting in ECU
( they may have to swap to fixed time rather than duty time based )
they may need REVERSED polarity of signal ( pretty sure that an MSD definite )


for the latter
- more dwell ( see the fixed V duty argument above )
- more V ( step up tranny ETC )
- swap to a non waste-spark sequential leading ignition to DOUBLE coil charge available periods

 

I have this exact same problem. does anyone have any resolve?

 

I have just earthed my battery from the boot to the engine bay with very thick wire. this has helped but teh ignition still breaks up quite badly, any ideas

 

Ther are alot of threads on this but now one ever communcates their solutions. Ill try and sort miune next week and let you all know what i did and what did or didnt work