Misfire On Boost At 4000rpm - Another One

[GUN32R]

Guys, I have posted this problem before but I am just not getting anywhere - 4 trips back to machanic, hours on the dyno but no luck

Took car to very reputable mechanic following done:

R32 GTR with Link G4 just installed, 700 cc Sard, Adj cam gears

It has splitfires and iridium plugs, runs Eboost 2 at 18psi

Car developed a very bad missfire only days after getting it back. Mechanic also said engine rings were on the way out (engine was rebuilt 7000km ago 3500km before i bought it).

I get a bad misfire from about 3800 to 5500, it revs well up until then 3800 and after 5500.

Things we have tried:

1. We have changed the ignitor a number of times - no difference
   
2. Changed coils - no difference
   
3. Changed plugs - no difference
   
4. Put on a power FC - no change
   
5. AFM's have been unplugged as G4 doesnt need them - no difference
   
6. Tried new loom - no difference
   
7. Checked connections with amp and all look good
   

Problem goes away once i get the engine really warm (way above normal temp - as if you have been boosting it heaps etc) - but i think this is because the mechanic has programmed the G4 to put more fuel into the engine at that operating temp at that specific rev range.

With the knowledge that programming the G4 to put more fuel into the car at certain temps and certain revs - can you guys suggest we try something else.

Only had a GTR for 6 months and I am getting close to torching it.

I have also thought of testing the following.

• Air leaks from intercooler
  
• Fuel pump
  

[pipster11]

ignitor pack?

and the grounding to it?

[R31Nismoid]

Ignitor and/or CAS

Also, what gap on the plugs? Were the plugs pre-gapped or manually done yourselves?

Why not use coppers?

[The Dan]

You did all that stuff and not tested the fuel pump or replaced fuel filter?

That's kinda the first thing you would do. The heat thing has to do with enrichment vs temp and if it get's slightly hot, it adds more fuel.

Definitely sounds like you have fuel issues.

[paulr33]

your peak torque is probably made around the 3800 to 5000 range but peak power is probably after 5000rpm

so the engine would likely use more fuel, need more spark etc past 5000rpm so i wouldnt put it down to something like lack of fuel (unless not tuned correctly) or break down of spark. id put it down to something mechanical. id be checking what the guys have said, check the fuel rail, pressure under load, check the simple stuff