R32 GTR Lean popping hesitation issues. Plaese help I'm going insane.

[needavdub]

Ok guys, I've been reading and working, and spending money, and working, and reading, and spending more money and I still can't fix this damn car. At the beginning of the summer I was having the notorious RB hesitation/misfire under boost at WOT. After doing the checklist found in the "fix your hesitation" thread I determined I needed to upgrade my coil packs. I installed a set of brand new Yellow Jackets and the car ran excellent, 16psi of boost and it pulled HARD to redline. It ran like that for about a month, then one day it started messing up. I did a 2nd gear pull and it started popping/misfiring like crazy, I turned my boost controller off (takes it to 10psi) and it at least ran ok-ish. But it still had a tendency to "chug" and miss at higher RPM. Seeing how it was a sudden change I figured something failed, so I replaced the fuel pump with a Denso 290lph unit that I "hotwired" for 14.4v all the time, replaced the fuel filter, cleaned and resoldered the MAF's. The problem still persisted. My coil pack harness was in very poor condition so I thought maybe that was my problem, so last night I installed a brand new one, along with new plugs. Still no luck, I checked my TPS voltage and it seemed to be off a bit, 3.3v at WOT, I adjusted it to 4.2 at WOT and .4 fully closed. I've checked for vacuum leaks, none seem to be present. The only thing I can figure now is a fueling problem (maybe fpr), when I did a hard pull with the boost controller set at 15psi last night it started "popping" and missing and my AFR's were lean at 13:1.

I'm really running out of ideas here guys... Please help me.

[nimblestix]

13.1 isnt really lean. Anything under 14 in boost is considered okay!
Check for boost leaks with a compresdor. Google or youtube "boost leak tester"

Good luck. Missing issues suck hard

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[needavdub]

I've always been told that 12:1-ish was "safe". My car used to be about 11.9:1 under full boost so 13:1 seemed lean. I'll check into boost leaks with pressure though, I kind of half-assed checking by using carb cleaner. I just sprayed it near any potential leak area and listened for a change in RPM. Thanks

[xcye]

Seems to be ignition problem again, since mis-firing creates lean condition.

[GTRADDICT]

Good heat range in plugs? Correct gap for 16 psi?

[Skym]

RB hesitation/misfire under boost at WOT.

Spark plug gap (factory is 1.1mm and need 0.8mm), use correct heatrange (NGK PFR7A minimum, PFR6A is factory) and get your ECU retuned. Running higher boost levels without retuning ECU is asking for trouble.

Also if sparkplug gap was still wide with new coilpacks and heatrange of sparkplugs not changed, then new coilpacks could be damaged.

Under boost 11.6:1 is a safe A/F ratio. Anything above 12.0:1 under boost is quite lean for stock engine. 13.0:1 A/F ratio is very lean and stock ECU probably would be pulling ignition timing in midrange to stop engine knocking.

With these mods (ECU retune, Z32 AFM's, injectors, etc), should be just below or over 400awhp with stock turbo's.

[needavdub]

I always use NGK BKR7's copper plugs gapped at .8mm. And I understand needing a tune, and that's on the list this winter (Right now I have a off the shelf Blitz tuned ecu, and steel wheel'd stock turbos). But the car ran awesome at 15-16psi for well over a month with no issues before this problem started, so I'm pretty sure something "broke". Ignition miss can cause a lean condition? I would have thought all the fuel with no spark would read rich? Maybe my ignitor then? There's not many ignition components left to replace haha.

[xcye]

I always use NGK BKR7's copper plugs gapped at .8mm. And I understand needing a tune, and that's on the list this winter (Right now I have a off the shelf Blitz tuned ecu, and steel wheel'd stock turbos). But the car ran awesome at 15-16psi for well over a month with no issues before this problem started, so I'm pretty sure something "broke". Ignition miss can cause a lean condition? I would have thought all the fuel with no spark would read rich? Maybe my ignitor then? There's not many ignition components left to replace haha.

Mis-firing normally creates lean condition, since the O2 sensor would pick up more unburned O2 than normal, therefore it would report a lean condition.

[needavdub]

Well I just found a bad injector connector, if I wiggled the wires near the injector it would misfire. I have a new one to splice in tomorrow. I really hope this fixes it, but I fear it's just another fault I'm finding along the way to actually fixing the problem....

[Rides]

i'm having the same issues with my car. please update if you find a fix. I've changed and clean mafs, clean aac, changed ignitor and new plugs. still having mis-fire at low rpm. Mine wants to stall at around 2500-3000 rpm. Today it actually stalled out while i was on 2nd gear. Had to start it back up as it was still rolling at 40km/h.

[needavdub]

Ok I'm really pulling my hair out now. I decided to eliminate any potential spark loss issues. So last night I installed another fresh set of NGK copper BKR7's gapped to .8mm, examined all my NEW yellow jackets, and NEW coil pack harness, and finally installed a different ignitor known to be good. I also replaced a bad injector connector and reset the computer. IT STILL MISSES!!!!!!@@!!! Why? I'm really running out of ideas here.

Right now the best thing I can think to do is pay for a data logging program like conzult and do a few pulls to see what the sensors are saying, does this seem like the logical next step? Could bad injector cause this? Please help me!

[rolyaT]

A miss could be from no fuel (bad injector). No juice = No boom mang. Also low cylinder compression and bad head gasket can cause a miss. GL

[Skym]

I agree, have seen a blown metal headgasket on RB28. The seal around cylinder failed and before removing headgasket, engine was missing at idle. Compression test should tell you if headgasket is leaking.

Another is blown intake gaskets (common on RB20, RB25, RB26 which makes engine go lean, but revs usually go up and down due to o2 sensor + ECU making engine rich, lean, ECU adjusting timing to suit if leak is really bad).

[needavdub]

Well last night I replaced all 6 injectors with 550cc's and replaced the computer with one tuned for the 550's. No change really, AFR's a bit richer but still missing ONLY @ WOT above 6k RPMS. Compression is 155 PSI acrossed all 6 cylinders. The car idles fine and doesn't seem to have any vacuum/intake gasket leaks. I checked by spraying carb cleaner on all potential leak areas while the car was running, no change in idle speed so no leaks. I still need to pressure test for boost leaks, but I'm really running out of ideas now.

[Skym]

Have you checked on exhaust side of engine??? Especially on front 2 and rear 2 cylinders.

One thing it could be is valve bounce at higher rpm due to weak valve springs or cambelt timing is out, lifter / shim clearances need to be checked. Could explain the lean, missing problem above 6000rpm. Valve bounce is fairly easy to spot as get black marks on base circle of camshafts (remove cam covers or look down oil cap hole with torch).