Mysterious Pfc Missfire In An R32 Gtr

[Cubes]

I have recently went from an AP Engineering PowerFC in my R32 GTST that was running 100% fine/no cuts jolts nothing to a 8.04a Rb26 PFC. The issue I described above in another post within this thread was not related to to the 'bug'.

So.... I am now feeling this damn BUG. lol. It most definitely is ECU and ECU ONLY related as if I were to plug the AP Engineering PFC back in it would never cut/jolt. Plug the RB26pfc in and there it is; always on light throttle!!!!!

I too have been told about the 'bug' from my workshop.

I guess I'll learn to live with it; its not all that bad as it doesn't always do it.

Appears to be the 8.04a version. Also note nothing on the car has changed apart from the ECU. It IS!!! the RB26 PFC.

[Burgerman]

I've got the same problem with my R32 GTR with apexi PFC. I had a much worse problem with a mines chipped standard ECU whereby it was cutting out on boost. With the PFC it does exactly as many other members here have described. A jolt-like missfire that can happen almost anytime anywhere but usually under light acceleration. My mechanic has pulled his hair out trying to find the problem and it's a relief to see some solutions here other than replacing things in hope it fixes the problem (=$$$). Will try the earthing thing and if that doesn't help i'll try a new TPS. Cheers for the help I just can't figure out why I didn't come across it when i was doing searches months ago :S

[0piston]

I was looking for PFC ign dwell times for my GTR and ran into this, I was just going to post how familar this was to a FD issue with a stock ECU--basically a internmittant hesitation and jerking, and suggest a fix was to run more grounds...or oddly enough also to go standalone ECU such as a PFC

[B0oStEr]

If improving earths around the coils and igniters fixes this problem the question remains 'why does the problem go away with the stock ecu?'

Could it be a case of there being an earth path through a pin in the stock ecu that is not present in the pfc?

Or is it a case of a hiccup in the ign./fuel map of the pfc that causes a miss but the miss is masked by a better spark that results from the earthing improvements?

[Cubes]

I've had a stock r32 rb20det ecu with no issue, ap engineering rb20det pfc with no issue, plugged the 4.08a gtr pfc in and the jerk occurs; plug the ap pfc back in and nothing

Its the 4.08a gtr pfc bug.

[Burgerman]

yeah i'm starting to pull my hair out on this one, i have re-earthed everything and to no avail. is there anything that can be changed with the software? such as re-flashing it? and then re-tuning it? if so I'm willing to do that as the only other thing that I can think would be an issue would be the TPS. but when I had my old ECU it didn't do this.....

[RussianE39]

Hi from Subaru world, Power FC for Subaru Impreza GC8 Ver 1-2 have this problem too, it is totally random misfires, one of our customer splitted his crankshaft to two halves after that PowerFC misfires, the most interesting thing, that Power FC's for Ver 3-4 or Ver 5-6 Imprezas haven't that bug. We tried everything - even totally new engine wiring harness - no luck, on stock ECU it drives fine, on PowerFC - pop-pop-boom-misfire :-(

[hippie]

Hmm all very interesting i have a similar prob in my gtr running a pfc not sure which version but i'll check i have heard that the pfc puts more load on your ignitor box than a standard ecu hence why when you switch ecus back the problem goes away and having a decent earth to your ignitor box will help aswell the factory earth is so tiny i think i'll get a grounding kit as i used to have one with a volt stabiliser but had to pull it out as it was flattening the battery and i didn't have the miss problem when i had it installed i also noticed when my car does the miss thing voltage readings on the pfc drop by like 2ish volts then come straight back up to normal

[Beer Baron]

I can add a bit more to this. my 32 GTR, 8.04a PFC. didn't have this problem for about 2 years. then one day it started. does it very, very rarely though. less than once a week. my other 32 GTR. just got it. built in japan (and I mean just built end of last year), got all the fruit on it inc a PFC 8.04a (bought brand new too) and it has the phantom miss/hesitation occaisionally. I'd say every 3rd time I drive it. I haven't done the re-earth the ignitor trick but I will do it soon.

[paulr33]

Hi from Subaru world, Power FC for Subaru Impreza GC8 Ver 1-2 have this problem too, it is totally random misfires, one of our customer splitted his crankshaft to two halves after that PowerFC misfires, the most interesting thing, that Power FC's for Ver 3-4 or Ver 5-6 Imprezas haven't that bug. We tried everything - even totally new engine wiring harness - no luck, on stock ECU it drives fine, on PowerFC - pop-pop-boom-misfire :-(

i dont know anything about the subura pfc version but its possible the same logic/code is used

do you know if you can apply the same fix scott used on the wrx to correct the misfire bug?

its in the powerfc faq in my signature, have a look for "misfire" the official fix is there

[Swiper the Fox]

ive never experienced this phenomenon.

dont think i ever drove at light throttle though.

[RussianE39]

I'm trying to fix that problem for about last 2 years, this is my opinions:

1) Problem is no way related to ignitior (at least on Subaru's)

2) In Subaru case PowerFC loses sync to camshaft / crankshaft sensors (In some very bad cases you could even see 16384rpm or smthing on Commander)

3) 90% of GC8 Ver 1-2 owners hadn't this problem when their PowerFC was new.

4) Some cars got it only on heavy load, under WOT etc, some cars got it only on light load.

I think we should compare input schematic for crankshaft sensor from non-affected PowerFC units with our misfiring units - 99.9% the problem is here.

2PaulR33, I found link to this thread in your FAQ, but haven't seen fix by scott, please point me. Ah, sry, that ground for ignitior is just placebo in case of Subaru :-)

Edited April 30, 2008 by RussianE39

[Cubes]

I'm trying to fix that problem for about last 2 years, this is my opinions:

1) Problem is no way related to ignitior (at least on Subaru's)

2) In Subaru case PowerFC loses sync to camshaft / crankshaft sensors (In some very bad cases you could even see 16384rpm or smthing on Commander)

3) 90% of GC8 Ver 1-2 owners hadn't this problem when their PowerFC was new.

4) Some cars got it only on heavy load, under WOT etc, some cars got it only on light load.

I think we should compare input schematic for crankshaft sensor from non-affected PowerFC units with our misfiring units - 99.9% the problem is here.

2PaulR33, I found link to this thread in your FAQ, but haven't seen fix by scott, please point me. Ah, sry, that ground for ignitior is just placebo in case of Subaru :-)

RussianE39,

When I had mine on the dyno last we tried to track down the issue. Datalogit... nothing showed in the logs. PFC h/c absolutely nothing showed. No spike or dip in rpm etc absolutely nothing. All sensors read outs etc were spot on.

All though it does sound similar it looks as if the suby's have got it considerably worse.

[jenkies]

just thought id add my experience. ive previously used a power FC in a GTR and it did the same 'miss' when cruising at light loads, say, every couple of days. sort of felt like the CAS was cutting out. wasnt like a slight 'pop' miss either, more like a hard jolt

I can add a bit more to this. my 32 GTR, 8.04a PFC. didn't have this problem for about 2 years. then one day it started. does it very, very rarely though. less than once a week. my other 32 GTR. just got it. built in japan (and I mean just built end of last year), got all the fruit on it inc a PFC 8.04a (bought brand new too) and it has the phantom miss/hesitation occaisionally. I'd say every 3rd time I drive it. I haven't done the re-earth the ignitor trick but I will do it soon.

i cant drive since i had pfc installed but had friends drive it and it worries me grrr

[Betz]

mine does it aswel, not sure on model number.

This is just a hunch, I have a feeling it could possibly be the unit doing a data dump or memory dump of logged engine data to an EPROM or onboard memory chip.

just a guess.

I'll be turfing the basic PFC when new engine build gets under way, may use D-Jetro if it doesnt suffer this problem, otherwise its MoTec and 2minute noodles for 6months

[RussianE39]

Anyone got digital oscilloscope ? I can easily see spikes / random noise on TACHO output of PFC on subaru when misfire occurs, my experience tells me this is problem with crankshaft sensor sync.

[Burgerman]

It might be something that is different for everyone. It might require different fixes for different people. For me I'm almost convinced it's an electrical problem. I've recently replaced a cracked battery terminal and have noticed that it does it less often. might sound rather qualitative however it was doing it before say 2 times a day (and I would drive maybe 20 mins a day?) whereas now it has done it once in the last week, and was very minor. I'm going to keep an eye on it, if it gets worse or still bothers me I'll look at getting a grounding/earthing kit from HKS installed.

Cheers guys and GL with your fixes

[Cubes]

Don't count your chickens before they are hatched.

It is a PFC issue.

Before I pulled mine off the road for a little work mine hadn't done it for 2 weeks. Then just as I was driving up near home to park the car for a couple of months it gave me a little miss. lol.

It comes and goes; you think its gone then its back again.

I've ran an RB20det pfc prior and not a zip... Drop rb26 pfc in and experience the dreaded miss; rb20det pfc back in and nothing.. Its the 8.04a PFC and well known amongst tuners who have a lot to do with the pfc.

[Burgerman]

I'm hoping to get some mods and a tune done later in the year so I'll keep an eye out for it and see if it gets worse or better. if worse I'll try the grounding/earthing kit.

for now if it miss-behaves I just tell the concerned passenger that I either ran over something or pretend nothing happened

[Rowdyr32]

From my experience and Scotsman who spoke to racepace a while ago. He said ben said some pfc's do it and some don't. It seems to happen when the pfc jumps out of or into closed loop - using the o2 sensor. You can stop it by turning the o2 sensors off I have been told.

Didn't read the whole thread though. Am I close??