My Rb25Det Problem Child. 5000Rpm And Vct

[benji-nz]

Hey guys

Having some trouble with my motor. Its a standard rb25det with FMIC, stock turbo, wasted spark, j30 ignitor, stock RB25DET auto ecu on manual trans, atmosphere bov, full decat 3 inch exhaust, walbro 255 fuel pump 14v and sard FPR, no VCT.

I installed a wideband temporarily in the o2 port to test AFR, as the problem exists with and without the o2 sensor connected.

The car seems to idles and free rev fine, and has no trouble with "town driving" (afr 13.3ish no o2 sensor)

In 2nd gear rising to WOT the car will hit 5000ish rpm (80km) and loose power, splutter, but not shudder. The Afr drops to 9 at that point.

The spark plug condition for all 6 plugs was and has stayed brown, with just a touch of white Ie no sign of a fowling or lean conditions with each periodic check, but maybe the journey home is covering the true spark plug condition? Plug gap is 0.80

Boost pressure has stayed at 5psi even with the intercooler and exhaust (unsure if id see a change or not) on the factory and aftermarket gauge.

Base timing looks to be 15 btdc, although this is after i retarded the cas as it was fully advanced. I did not check the timing beforehand

but the problem did still exist.

I did also notice the boost control solenoid wire has been run individually but to who knows where, was there is no solenoid on the turbo, just a connector or reference pipe from wastegate to turbo front.

An additional problem has to do with the VCT. When i bought the car it was disconnected. When i attached the plug, it would idle, but any throttle action caused a severe shuddering. On inspection the 113 port was connected correctly, but it appears (RB20 loom used i believe so dodgy wires everywhere) that the "power" wire was being taken from a Injector connection on the ecu side, with solder. Is the interferrence of this power sauce causing the injector to loose signal, or would have no affect as the rpm switch point was no where near the activation rpm required?

Any help would be great.

Cheers!

[Rolls]

Sounds like you have dodgy loom/wiring, get the entire loom sorted first then plug in a consult cable and find out what sensors are "Failing" and get them fixed/re wired as it is most likely a wiring problem.

Regarding the misfire that explains why it is going rich at high rpm, a miss will make AFR drop massively, almost certainly f**ked coilpacks failing and causing the issue like the other 9000 people with this problem do a search as there are about 10 threads 40 pages long with the same issue. Short answer is you have weak spark, decreasing spark gap helps fix the problem, also making your motor not run as rich (retune) will help fix problem as leaner mixture is easier to ignore.

You may have an intake leak causing the motor to run excessively rich, this will exasperate the misfiring problem as you now have a harder to ignite richer mixture.

Best of luck.

Edited August 18, 2013 by Rolls

[benji-nz]

Hey Rolls

Yes I did have a read through those Misfire threads, but I felt it may be of another origin. Then again that might just be blissful ignorance! I will build a boost leak tester, and unless some god awful leak appears ill look into a new coil pack for the wasted spark. In saying that the coil pack did have acceptable conductivity and resistance, though as to whether that reflects on actual performance I suppose is another thing entirely?

Cheers!

Oh and as for the consult. Is it likely to show anything else that doesnt get registered with the old paper clip/engine light trick?

[Rolls]

It will show the same error codes, if you replace the coil packs get yellow jackets or splitfires, dont go wasted spark.

[Ben C34]

What dwell do the coils you have actually require? I have read a few threads of guys with wasted spark setups on stock ecu with misfires. I find it hard to believe it would be the same as stock. I changed to ls coil packs, on stock dwell there was a miss, sort out dwell and miss gone.

[benji-nz]

To be honest i am unsure of the dwell on the coilpack. The thing is i believe it worked fine (if im remembering correctly) when I purchased the car, but it had a different ignitor at the time (silver early model one 22020 05U00) This ignitor had a faulty ground and was replaced with a "j30" one which involved a wiring switch. Whether that has made a difference im unsure as the car was not driven hard for a while, as other issues reared there ugly heads.

On the note for a Loom, i did infact purchase an RB25DE loom from a R33 GTS25 auto a while ago but on inspection it appears the "body loom"? is different to the R32. On the DE loom there is a main blue ecu plug, and a white large elongated one. On the current loom in the R32, which is unknown, there are atleast 4 or 5 seperate plugs that appear to be wired in. As to where they go I have no clue!

Ill post up some picks up the loom to highlight what I'm meaning.

GTS25 RB25DE loom

R32 Loom (unknown but probably RB20DET)

Edited August 21, 2013 by benji-nz

[Badgaz]

Get new looms plugs and ecus at www.rbparts.co.nz ...... Plugs should be gapped 0.8mm they are usually the cause of this problem.

Edited August 24, 2013 by Badgaz

[benji-nz]

So have begun the task of finding the fault. I tested the Ohm resistance (20k) from the ECU to the Plug into the ignitor, and cylinders 1-3-4-6 all had a 0.00 or 0.01 resistance. Cylinders 2-5 (pins 2 and 12) has 0.94 or 0.93 ohms. Could this be enough to cause a miss at the higher RPM?

[Rolls]

Do they have scalding on the outside indicating the spark is jumping to the block?

[benji-nz]

No scalding that I can see.

[benji-nz]

Little update.

VCT is fixed. Rewired it with a new plug, and a standalone power source and is all go! What a difference!

The issue with the fuel ratio was with the o2 sensor unplugged. Plugged in and with the wideband in the exhaust, had 14.7 afr at cruising.

Thirdly the car still has a miss, link to the video here;

One is around 25 seconds, the other 'fart' at 55 seconds.Again around 5000 rpm/2nd gear

Still like the typical RB miss?

Edited September 8, 2013 by benji-nz